ArticlePDF Available

Lunar cycle in homicides: A population-based time series study in Finland

Authors:

Abstract and Figures

Objective To test whether homicides in Finland vary according to moon phases. Design A time series study. Setting Finland. Participants 6808 homicides committed in 1961–2014. Outcome Daily numbers of homicides. Method The daily numbers of homicides were related to eight moon phases and the illuminated percentage of the moon disc using negative binomial regression. To identify lunar patterns, piecewise linear terms of lunar days were used, together with changes from one moon phase to another. Homicides were similarly regressed on quintiles of the illuminated percentage of the moon disc. A periodic term of length 29.53 days was included to detect cyclic patterns. The results were adjusted for sex, age, secular trend, distance from the moon, seasons, weekday, major holidays and temperature. Results During the full moon, 15% less homicides were committed than during the new moon (RR 0.85; 95% CI 0.77 to 0.94) and 86% less during the lightest quintile of illumination compared with the darkest quintile (RR 0.14; 95% CI 0.04 to 0.50). Adjustments did not change the results. Piecewise linear regressions showed a significant decline in homicides at the full moon and a rise thereafter. The full moon drop in homicides was directionally similar for seasons, weekdays, sex, age and time periods, and it was particularly pronounced in the early part of period studied (1961–1974). Periodic regression showed a regular cyclic pattern of length 29.53 days (p~0.035). Conclusions Contrary to current scientific opinion, an association exists between moon phases and homicides, and contrary to what has been previously assumed, homicides declined during the full moon, especially in earlier decades. However, the causality of the association remains elusive.
Content may be subject to copyright.
1
NäyhäS. BMJ Open 2019;9:e022759. doi:10.1136/bmjopen-2018-022759
Open access
Lunar cycle in homicides: a population-
based time series study in Finland
Simo Näyhä
To cite: NäyhäS. Lunar
cycle in homicides: a
population-based time series
study in Finland. BMJ Open
2019;9:e022759. doi:10.1136/
bmjopen-2018-022759
Prepublication history and
additional material for this
paper are available online. To
view these les, please visit
the journal online (http:// dx. doi.
org/ 10. 1136/ bmjopen- 2018-
022759).
Received 9 March 2018
Revised 23 October 2018
Accepted 5 December 2018
Faculty of Medicine, Center for
Environmental and Respiratory
Health Research, University of
Oulu, Oulu, Finland
Correspondence to
Professor Simo Näyhä;
simo. nayha@ oulu. 
Research
© Author(s) (or their
employer(s)) 2019. Re-use
permitted under CC BY-NC. No
commercial re-use. See rights
and permissions. Published by
BMJ.
ABSTRACT
Objective To test whether homicides in Finland vary
according to moon phases.
Design A time series study.
Setting Finland.
Participants 6808 homicides committed in 1961–2014.
Outcome Daily numbers of homicides.
Method The daily numbers of homicides were related to
eight moon phases and the illuminated percentage of the
moon disc using negative binomial regression. To identify
lunar patterns, piecewise linear terms of lunar days were
used, together with changes from one moon phase to
another. Homicides were similarly regressed on quintiles
of the illuminated percentage of the moon disc. A periodic
term of length 29.53 days was included to detect cyclic
patterns. The results were adjusted for sex, age, secular
trend, distance from the moon, seasons, weekday, major
holidays and temperature.
Results During the full moon, 15% less homicides were
committed than during the new moon (RR 0.85; 95% CI
0.77 to 0.94) and 86% less during the lightest quintile of
illumination compared with the darkest quintile (RR 0.14;
95% CI 0.04 to 0.50). Adjustments did not change the
results. Piecewise linear regressions showed a signicant
decline in homicides at the full moon and a rise thereafter.
The full moon drop in homicides was directionally similar
for seasons, weekdays, sex, age and time periods, and
it was particularly pronounced in the early part of period
studied (1961–1974). Periodic regression showed a
regular cyclic pattern of length 29.53 days (p~0.035).
Conclusions Contrary to current scientic opinion, an
association exists between moon phases and homicides,
and contrary to what has been previously assumed,
homicides declined during the full moon, especially in
earlier decades. However, the causality of the association
remains elusive.
INTRODUCTION
A number of studies have tried to identify
lunar variations, the so-called ‘Transylvania
effect’1 in various types of human activity such
as aggressive behaviour,2 assaults, crime,3 4
homicides,5–9 traffic accidents,10 suicides9 11
and mental disorders.12 One line of thought
has been that gravitational forces, which are
greatest during the full moon and the new
moon, would cause cyclic fluid shifts between
body compartments and thereby trigger
emotional disturbances, suicides and aggres-
sive behaviour in predisposed individuals, as
stipulated in the theory of ‘biological tides’.7
Other theories have considered moon-re-
lated variations in electromagnetic fields,13
weather14 and illumination15 16 as potential
factors, which could affect human behaviour
and cause adverse health effects.
While the belief in lunar effects on humans
is reportedly common, especially among
healthcare personnel12 17 18 and police,19 it
is not well supported by empirical evidence.
Studies claiming such effects are said to be
poorly conducted due to questionable data
analysis, insufficient sample size, too short
periods studied, data dredging or uncon-
trolled confounding by season, weekdays or
holidays,12 20–24 and their findings have not
been replicated in other populations.6 19 22 A
comprehensive review14 concluded that not
even in theory can lunar factors interfere with
human behaviour and discouraged further
studies, as did some reviews and meta-anal-
yses.19 20 Thus, human beings would be imper-
vious to lunar effects,25 perhaps excepting
the trivial fact that some activities are easier
in moonlight14 and accidents more likely to
occur during the dark new moon nights.26
While many earlier works have studied
potential effects of the full moon on aggres-
sion and homicides,5–9 27 few studies have
addressed this particular topic nowadays,3 12 all
with negative or equivocal results. The present
paper sets out to retest the hypothesis that no
association exists between the lunar cycle and
Strengths and limitations of this study
The analyses were controlled for potential con-
founding by sex, age, secular trend, distance
from the moon, seasons, weekdays, holidays and
temperature.
The data comprised a long time series from a na-
tional population.
Limitations include that the exact time of death
was not known, and homicides could not be broken
down topremeditated murders and manslaughters,
which may have different patterns.
The association observed does not imply a causal
relation between the moon phases and homicides.
on 15 January 2019 by guest. Protected by copyright.http://bmjopen.bmj.com/BMJ Open: first published as 10.1136/bmjopen-2018-022759 on 15 January 2019. Downloaded from
2NäyhäS. BMJ Open 2019;9:e022759. doi:10.1136/bmjopen-2018-022759
Open access
homicides. The data comprise a 54-year time series of
homicides in Finland, which is subjected to linear spline
and periodic regressions to identify any lunar patterns.
METHODS
Data
The daily numbers of homicides in Finland during
the period 1961–2014, classified by sex and age group,
were obtained from Statistics Finland, the study period
consisting of 668 lunar synodic cycles. The cases were
defined as those deaths where homicide was recorded as
the underlying cause (in 1961–1968 ICD-7 codes E964
and E980–E984; in 1969–1986 ICD-8 codes E960–E969;
in 1987–1995 ICD-9 codes E960–E969; in 1996–2014
ICD-10 codes X85–Y09 and Y87.1). Annual populations
were obtained from official statistical sources. Informa-
tion on mean daily temperatures in 13 weather stations
representing all regions of the country (South: Helsinki,
Juupajoki, Kaarina, Lahti; Central: Seinäjoki, Jyväskylä;
East: Mikkeli, Joensuu, Kuopio, Kajaani; North: Oulu,
Rovaniemi, Sodankylä) was obtained from the Finnish
Meteorological Office, missing observations (0.1%)
being estimated by cubic spline regression with 3 df. Due
to small daily numbers, no analysis by region could be
conducted, and instead daily temperatures were averaged
over the weather stations.
Statistical analysis
The daily counts were linked to eight lunar phases (new
moon, waxing crescent, first quarter, waxing gibbous, full
moon, waning gibbous, last quarter, waning crescent).
The approximate days of the lunar synodic cycle were
calculated based on radians (1 lunar day=2π/29.53).
Since the lunar synodic cycle is slightly irregular, with vari-
ation from 29.18 to 29.93 days, the illuminated percentage
of the moon disc (0%100%) was used as an additional
explanatory variable. All measures were obtained using
the lunar package available in the R software.
Crude homicide mortality by lunar phases was first
expressed as the number of homicides per 100 000
person-years. Then the daily counts were regressed on
eight lunar phases (a categorical variable), adjusting
for sex, age (in classes 0˗14, 15˗64, 65+ years), secular
trend (a third-degree polynomial), distance of the
moon from the earth (in classes apogee, far, average,
near, perigee), seasons (Winter: December to February;
Spring: March to May; Summer: June to August; Autumn:
September to November), weekdays, those public holi-
days which showed association with homicides (New
Year, Midsummer Eve, Midsummer Day, Christmas Eve)
and temperature. To allow for extra-Poisson variation
caused by more than one person dying in the same inci-
dent, negative binomial regression was used. The good-
ness-of-fit test (the goodfit function in R) first showed a
poor fit of daily homicides to negative binomial distribu-
tion (p~0.000), but after removing two outliers (8 and
10 school shootings committed by a single perpetrator
each), the fit improved (p~0.124). All regressions were
run with and without exclusion of these outliers, but the
results were practically identical, and only results without
exclusions are shown. The link function used was loga-
rithmic, and the results were expressed as rate ratios (RR)
and their 95% CIs.
The lunar association of homicides was also examined
by regressing daily homicides on linear splines of lunar
synodic days, using midpoints of moon phases as knots.
This analysis retained the continuity of the explanatory
variable (lunar day) but allowed for non-linearity of the
association and also enabled piecewise comparisons of
regression slopes and their changes from one phase to
another. Homicides were similarly regressed on linear
splines of the illuminated proportion of the moon disc,
using quintile points of the illuminated percentage as
knots, with a further study of changes of piecewise regres-
sion slopes between the quintiles. To reveal any regular
lunar cyclicity in homicides, the daily counts were treated
as a time series of 19 723 days, fitting a periodic term
of 29.53 days in length, together with other periodic-
ities (1 year, ½ year, 1/3 year, 1/4 year, 1 week and 1/2
week). The calculations were performed using R, V.3.1.0
(R Development Core Team, 2014, available at: http://
www. R- project. org) and Stata, V.11 (StataCorp, College
Station, Texas, 2009).
Patient and public involvement
No patients were involved in this study.
RESULTS
Descriptive data
The mean daily number of homicides was 0.35 (range
0–10) and mortality was 2.54 deaths per 100 000 person-
years (table 1). Altogether, 751 homicides were committed
during the full moon, compared with 831–895 during
other lunar phases, with respective mortalities of 2.24 and
2.48–2.68 per 100 000 person-years. The distribution of
days according to the illuminated portion of the moon
disc was very uneven, with strong accumulations on the
lightest and darkest ends of the illumination scale (figure
SF1 in the online supplementary file). During full moon
days, the moon was almost fully illuminated (96%–100%)
and during new moon days, the moon was almost fully
dark (0%–4%), while during all other phases, the illumi-
nated percentage was distributed over broader ranges,
that is, 26%–38% (table 1).
Homicides and moon phases
The left-hand panel of figure 1 compares crude homi-
cide mortality by moon phases using rate ratios obtained
from negative binomial regression with the moon phase
as a categorical explanatory factor. Compared with the
empty model (no explanatory factors), the p value from
the likelihood ratio test was 0.028, indicating some differ-
ence in mortality between the moon phases. In particular,
mortality during the full moon phase was 15% lower than
on 15 January 2019 by guest. Protected by copyright.http://bmjopen.bmj.com/BMJ Open: first published as 10.1136/bmjopen-2018-022759 on 15 January 2019. Downloaded from
3
NäyhäS. BMJ Open 2019;9:e022759. doi:10.1136/bmjopen-2018-022759
Open access
Table 1 Moon phases and homicides
Moon phase
(approximate
days*)
Percentageof
moon disc
illuminated
Temperature
(°C)† Days(n)
Homicides per
phase(n)
Mean number of
homicides per
day
Person-years ×
10 000
Mortality/
100 000 person-
years
Adjusted rate ratio (RR)‡
RR 95% CI
New moon (27.7–
1.9)
0–4 3.1 2467 883 0.358 3349.3 2.64 1.00
Waxing crescent
(1.9–5.5)
4–30 3.1 2465 889 0.361 3346.5 2.66 1.01 0.92to1.11
First quarter
(5.5–9.2)
30–68 3.0 2467 857 0.347 3349.3 2.56 0.97 0.88to1.07
Waxing gibbous
(9.2–12.9)
68–96 3.0 2461 895 0.364 3341.1 2.68 1.01 0.92to1.12
Full moon (12.9–
16.6)
96–100 2.8 2466 751 0.305 3347.9 2.24 0.85 0.77to0.94
Waning gibbous
(16.6–20.3)
70–97 3.0 2464 846 0.343 3345.2 2.53 0.96 0.87to1.06
Last quarter (20.3–
24.0)
32–70 2.9 2465 831 0.337 3346.5 2.48 0.94 0.86to1.04
Waning crescent
(24.0–27.7)
4–32 3.2 2468 856 0.347 3350.6 2.55 0.97 0.88to1.07
P~§ 0.015
Total 3.0 19 723 6808 0.345 26 777.1 2.54
*Days 0.0–29.5 calculated based on radians with the full moon cycle of 2π and 1 day corresponding 0.213 radians.
†Mean daily temperature.
‡From negative binomial regression adjusting for sex, age, secular trend (third-degree polynomial), distance from the moon, seasons, weekdays, public holidays (New Year, Midsummer Eve, Midsummer
Day, Christmas Eve) and temperature.
§From likelihood ratio test.
on 15 January 2019 by guest. Protected by copyright.http://bmjopen.bmj.com/BMJ Open: first published as 10.1136/bmjopen-2018-022759 on 15 January 2019. Downloaded from
4NäyhäS. BMJ Open 2019;9:e022759. doi:10.1136/bmjopen-2018-022759
Open access
that during the new moon (RR 0.85, 95% CI 0.77 to 0.95),
while during no other phase did RR deviate from the
reference level. The adjusted RRs (table 1, table ST1 in
the online supplementary file) remained almost similar
to the unadjusted ones.
Figure SF2 in the online supplementary file reviews
the consistency of the lunar pattern of homicides by
subgroups and shows an almost invariably low RR during
full moon across years, seasons, weekdays, sex and age.
The homicide dip during the full moon was particu-
larly steep in 1961˗1974 (RR 0.77; 95% CI 0.61 to 0.96)
compared with other periods, and it was also low among
women (RR 0.72; 95% CI 0.60 to 0.88), in spring (RR
0.79; 95% CI 0.64 to 0.97), autumn (RR 0.78; 95% CI
0.63 to 0.97) and in days other than weekend days (RR
0.82; 95% CI 0.71 to 0.95). However, all likelihood ratio
tests for interaction between lunar phase and these
stratification factors were non-significant at a 0.05 level,
indicating a failure to reject the null hypothesis that the
overall patterns are uniform over the strata.
Table 2 shows the piecewise regression slopes (change
of RR per lunar day) and their changes from one moon
phase to another. Just before the full moon, that is, on
approximate lunar days 11–15 (waxing gibbous to full
moon), the homicide rate declined by 6% per 1 lunar
day (RR 0.94; 95% CI 0.91 to 0.98), and immediately after
that, that is, on days 15˗19 (full moon to waning gibbous)
it rose again by 5% per day (RR 1.05; 95% CI 1.01 to 1.09).
A different parametrisation in the right-hand column
of table 2 shows that during the lunar days 11˗15, the
curve turned down by 8% (RR 0.92; 95% CI 0.86 to 0.99)
compared with the preceding interval (days 7–11), and
the upturn that followed during the next interval was
11% (RR 1.11; 95% CI 1.04 to 1.20).
Homicides and the illuminated proportion of the moon
Homicide mortality is also shown in relation to the illumi-
nated proportion of the moon disc in the form of linear
splines of the illuminated percentage (right-hand panel
of figure 1). Compared with the darkest stage (0% illu-
minated), the crude RRs remained relatively unchanged
over the quintiles I˗IV of illumination but declined
steeply during the lightest quintile, down to 0.84 (95% CI
0.77 to 0.92) at the fully illuminated moon.
The piecewise regression slopes (change of RR per one
percentage unit illuminated) in table 2 were not signifi-
cant in quintiles I–IV, but the slope parameter was signifi-
cantly small in the lightest quintile (RR 0.14; 95% CI
0.04 to 0.50), indicating a steep decline in homicides,
with the RR 90% smaller than that in the preceding quin-
tile (RR 0.10; 95% CI 0.02 to 0.53).
Periodic regression
Table 3 summarises the periodic regression of homicides
fitting the first-order sinusoid terms for the lunar synodic
cycle together with other periodicities and adjusting for
the secular trend. The periodicities of 6 and 3 months
proved insignificant at 0.05 level and were omitted. The
periodic components are shown graphically in figure
SF3 in the online supplementary file. The pattern is
dominated by wide-amplitude 7 and 3.5-day cycles, corre-
sponding to their large positive cosine and large negative
Figure 1 Rate ratio (RR) for homicides in Finland, 1961–2014, by moon phases (left) and by percentage of the illuminated
portion of the moon disc (right). The shaded area shows the 95% condence band of RR. The moon phases are: new moon
(NM), waxing crescent (WaxC), rst quarter (FQ), waxing gibbous (WaxG), full moon (FM), waning gibbous (WanG), last quarter
(LQ) and waning crescent (WanC). P values from likelihood ratio test: 0.028 for moon phases, 0.022 for percentage of moon disc
illuminated.
on 15 January 2019 by guest. Protected by copyright.http://bmjopen.bmj.com/BMJ Open: first published as 10.1136/bmjopen-2018-022759 on 15 January 2019. Downloaded from
5
NäyhäS. BMJ Open 2019;9:e022759. doi:10.1136/bmjopen-2018-022759
Open access
sine terms (table 3), with somewhat lower amplitude
1-year and 4-month cycles. The 29.53-day lunar cycle is
also significant and most influenced by its negative sine
term. The model-predicted composite pattern of homi-
cides incorporating all significant periodicities is illus-
trated in figure 2, together with the lunar periodicity
alone. The pattern is shown for the 538th lunar cycle
(14 August to 11 September 2004), during which homi-
cide mortality was close to the average mortality during
the whole study period. The lunar cycle is overshadowed
by the weekly swings but is still significant, the model-es-
timated peak and trough locating on approximately
second and 17th lunar days. The trough of the estimated
mortality curve was 9% lower than the estimated peak
(95% CI 5% to 13%).
DISCUSSION
Most studies on lunar effects on humans have produced
negative results, including those focused on homi-
cides,5 6 9 19 20 28 although some negative findings may
be due to type II error.29 Positive findings have been
reported for aggravated assaults,2 crimes,30 poison centre
calls,31 extremely violent behaviour17 and general prac-
tice consultations.1 The observations reported as positive
have been attributed to selective sampling, erroneous
definitions of lunar phases, too short periods studied,
flawed data analysis, confounding, type I error or data
dredging.6 14 20 The present study based on a time series
of 19 723 days and 668 lunar cycles found an unequivocal
lunar pattern in homicides that was not confounded by
sex, age, secular trend, distance from the moon, seasons,
weekdays, holidays or temperature, and the finding was
consistent across relevant subgroups. The analysis also
revealed a regular lunar pattern in homicides. Since
the data comprised the entire national population, they
cannot be distorted by biased sampling. The results
do not support the notion emanating from previous
research that no association exists between the moon and
homicides.
The study of Lieber and Sherin,7 based on two inde-
pendent samples from the USA, is sometimes referred to
as the only one to have observed a statistically significant
variation of homicides by lunar phases.20 The authors
linked homicides to lunar phases using time of injury,
but if time of death was used instead, the association
disappeared.8 Thus, the present study is the first one to
show that homicidal deaths vary according to the moon
phases. The pattern was still unexpected, since homicides
reduced during the full moon while a bimodal rise during
the full moon and the new moon was found in the above
study.7 Violent behaviour17 and aggravated assaults2 have
also been reported to increase during the full moon,
Table 2 Adjusted* rate ratios (RR) and their 95% CIs from piecewise negative binomial regression of homicides on lunar days
and on percentage of moon disc illuminated
RR† 95% CI
Relative change in RR versus
preceding interval
RR 95% CI
Intervals between midpoints (day) of moon phases
New moon (0) to waxing crescent (3.7) 1.00 0.95 to 1.05
Waxing crescent (3.7) to rst quarter (7.4) 0.98 0.94 to 1.02 0.98 0.91 to 1.06
First quarter (7.4) to waxing gibbous (11.1) 1.02 0.98 to 1.06 1.04 0.97 to 1.12
Waxing gibbous (11.1) to full moon (14.8) 0.94 0.91 to 0.98 0.92 0.86 to 0.99
Full moon (14.8) to waning gibbous (18.5) 1.05 1.01 to 1.09 1.11 1.04 to 1.20
Waning gibbous (18.5) to last quarter (22.1) 0.98 0.94 to 1.02 0.93 0.87 to 1.00
Last quarter (22.1) to waning crescent (25.8) 1.03 0.98 to 1.07 1.05 0.98 to 1.13
Waning crescent (25.8) to new moon (29.5) 1.00 0.95 to 1.05 0.97 0.90 to 1.05
P~‡ 0.047 0.047
Quintiles of illuminated percentage of moon disc
I (0.0% to 9.6%) 1.10 0.31 to 3.88
II (9.6% to 34.5%) 0.78 0.48 to 1.27 0.71 0.14 to 3.56
III (34.5% to 65.5%) 0.99 0.67 to 1.45 1.26 0.57 to 2.80
IV (65.5% to 90.5%) 1.34 0.82 to 2.19 1.36 0.61 to 3.00
V (90.5% to 100.0%) 0.14 0.04 to 0.50 0.10 0.02 to 0.53
P~‡ 0.011 0.011
*Adjusted for sex, age, secular trend (third-degree polynomial), distance from the moon, seasons, weekdays, public holidays (New Year,
Midsummer Eve, Midsummer Day, Christmas Eve) and temperature.
†Relative change per 1 day, or relative change per one percentage unit of illumination.
‡From likelihood ratio test.
on 15 January 2019 by guest. Protected by copyright.http://bmjopen.bmj.com/BMJ Open: first published as 10.1136/bmjopen-2018-022759 on 15 January 2019. Downloaded from
6NäyhäS. BMJ Open 2019;9:e022759. doi:10.1136/bmjopen-2018-022759
Open access
which is relevant here, since violence and assaults repre-
sent the same criminal act as homicide, except that
the victim survives. No previous study has found any
significant decline in homicides during the full moon,
although such declines have been reported for emer-
gency contacts,24 trauma,26 traffic accidents10 and alcohol
intake.32
Limitations of this study include the fact that homi-
cides were assigned to moon phases using the day of
death, while factors decreasing homicides during the full
moon would start to influence some time before that.
The resulting inaccuracy cannot be great, since approx-
imately 85% of homicide victims in Finland are found
dead or die within 24 hours.33 Comparable figures have
been reported from the USA6 34 and Europe.35 An addi-
tional source of error is that the exact time of the day
of the homicide was not known, since potential effects
of moonlight should be different by night and day.36 A
further limitation is that homicides could not be broken
down to premeditated murders and manslaughters, the
timing of which may be influenced by different factors.
Even though an association was found between the moon
phases and homicides, the study design and available data
do not allow any causal conclusions to be drawn.
Any positive findings based on empirical data may
be due to type I error, that is, a departure from the
null hypothesis when no true difference exists. This is
sometimes offered as an explanation for allegedly positive
findings in studies claiming lunar effects, especially those
failing to fulfil the criteria for causality, for example,
consistency of the finding across subgroups of the data.
The credibility of the present finding is corroborated by
the similarity of the pattern and its similar directionality,
in successive time periods, seasons, weekdays, in men and
women and different age groups, with the homicide drop
mostly occurring during the full moon. The decline in
homicides during the full moon was confirmed by phase-
by-phase analysis and by analysis of successive illumina-
tion quintiles. The possibility of a coincidental finding
is also reduced by the long time period, relatively large
sample size and the largest number of lunar synodic
cycles ever studied. In theory, it is possible that small
sample sizes in many previous studies have led to type II
errors, preventing any recognition of true effects.29
While investigations reporting an increase in adverse
human behaviour during full moon mostly refer to some
geophysical explanation,14 those observing a decrease in
such phenomena during full moon have had more diffi-
culty to explain their findings. Thus, studies noting a
decrease in emergency contacts24 and traffic accidents10
during the full moon did not contemplate the underlying
reasons at all, while de Castro and Pearcey32 assumed that
the decrease in alcohol intake with increasing moonlight
could be attributed to some moon-related biological
Table 3 Periodic regression of daily homicides, 19612014
Term Coefficient z
P value
foradding
terms*
Secular trend 0.000
x −0.631 −0.320
x2−25.944 −13.455
x3−5.127 −2.671
12 months 0.057
Sin(x) −0.018 −0.964
Cos(x) −0.040 −2.198
4 months 0.021
Sin(x) −0.051 −2.780
Cos(x) −0.005 −0.281
7 days 0.000
Sin(x) −0.051 −2.712
Cos(x) 0.172 9.564
3.5 days 0.000
Sin(x) −0.060 −3.276
Cos(x) 0.100 5.474
29.53 days 0.035
Sin(x) −0.038 −2.085
Cos(x) −0.028 −1.540
x=days 1…19 723.
*From likelihood ratio test.
Figure 2 Regular periodicity of daily homicides in
Finland assessed by periodic regression. Model-predicted
numbers of homicides during the lunar cycle 14August
to 11September 2004 are shown. Thin line describes the
multicycle periodicity composed of the lunar cycle (29.53
days; p~0.035), 12 months (p~0.057), 4 months (p~0.021), 7
days (p~0.000) and 3.5 days (p~0.000). Thick lines represent
the lunar periodicity alone (dashed lines: 95% condence
band). White circles indicate the observed mean numbers
and mortality of homicides during the entire study period.The
moon phases are: new moon (NM), waxing crescent (WaxC),
rst quarter (FQ), waxing gibbous (WaxG), full moon (FM),
waning gibbous (WanG), last quarter (LQ) and waning
crescent (WanC).
on 15 January 2019 by guest. Protected by copyright.http://bmjopen.bmj.com/BMJ Open: first published as 10.1136/bmjopen-2018-022759 on 15 January 2019. Downloaded from
7
NäyhäS. BMJ Open 2019;9:e022759. doi:10.1136/bmjopen-2018-022759
Open access
rhythm. A Dutch study26 noting a statistically significant
decline of 2% in traffic accidents during the full moon,
attributed this to better visibility due to moonlight, an
explanation regarded as trivial by some.14 As a brighter
environment may deter criminal acts,16 moonlight could
have played a role in the prominent full moon dip in
homicides in 1961˗1974 when one-half of Finns lived in
countryside compared with one-fourth nowadays when
most people live in cities and an artificially lit environ-
ment. However, the causal role of moonlight remains
unclear also because most homicides in this country are
committed indoors,33 and the actual lighting conditions
in each case were not known.
The seasonality of homicides with a summer peak,
potential bimodality and the changes in the pattern since
the 1870s has been reported previously,37 38 but no study
has decomposed the annual variation to shorter cycles.
The concentration of homicides to weekends and the
association with alcohol consumption is well known.39
The present study controlled for the effect of weekdays
but not for alcohol consumption in lack of daily data. Any
regular 3.5-day cycle in homicides has not been reported
previously and it warrants further study.
Why homicides decreased during the full moon is not
easily explained. One might speculate that the full moon,
so clearly perceived and distinguished from other moon
phases by virtue of its fully illuminated disc and short
duration, may have some superstition-based meaning
in peoples’ minds that refrains potential lunar phobic
perpetrators from committing the act. The belief that the
moon affects human behaviour is common among health-
care personnel, police17–19 and the general public.40 The
victim’s behaviour might play a role, too. As in most cases,
the victim and the perpetrator know each other and have
been in dispute before,33 potential homicide victims
who feel themselves threatened may avoid moonlight to
protect themselves, or they may believe that something
unfortunate could happen during the full moon. Some
might see the drop in homicides during the full moon
as an atavistic remnant from the animal kingdom where
certain prey animals suppress their activity in moonlight
to hide themselves from predators, or perhaps, their
enhanced visual acuity in moonlight would help them
detect predators.41 However, factors other than moon-
light may play a role as well.
CONCLUSIONS
Homicides in Finland follow a detectable and regular
cyclic pattern with a decrease during the full moon.
This decrease, applied to all moon phases, would imply
a decrease of approximately 20 homicides in an average
year, that is, a decrease of 0.38 homicides per 100 000
person-years, compared with the average of 2.54/100 000
during the entire study period. Irrespective of what the
underlying reasons may be, the prospects for prevention
are limited, as most people dwell in towns nowadays and
have less contact with the natural environment. Perhaps,
this was reflected in little variation in homicides in the
2000s. In any case, the finding challenges the current
scientific opinion that the lunar cycle and homicides are
unrelated, and it questions the widely held belief that the
full moon may provoke violent behaviour.
Contributors SN conceived the study idea, did all data analyses and wrote the
manuscript.
Funding Institutional funding.
Competing interests None declared.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The data are condential and cannot be shared.
Open access This is an open access article distributed in accordance with the
Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which
permits others to distribute, remix, adapt, build upon this work non-commercially,
and license their derivative works on different terms, provided the original work is
properly cited, appropriate credit is given, any changes made indicated, and the use
is non-commercial. See: http:// creativecommons. org/ licenses/ by- nc/ 4. 0/.
REFERENCES
1. Neal RD, Colledge M. The effect of the full moon on general practice
consultation rates. Fam Pract 2000;17:472–4.
2. Lieber AL. Human aggression and the lunar synodic cycle. J Clin
Psychiatry 1978;39:385–7.
3. Biermann T, Asemann R, McAuliffe C, et al. Relationship between
lunar phases and serious crimes of battery: a population-based
study. Compr Psychiatry 2009;50:573–7.
4. Schafer JA, Varano SP, Jarvis JP, et al. Bad moon on the rise? Lunar
cycles and incidents of crime. J Crim Justice 2010;38:359.67.
5. Pokorny AD. Moon phases, suicide, and homocide. Am J Psychiatry
1964;121:66–7.
6. Pokorny AD, Jachimczyk J. The questionable relationship between
homicides and the lunar cycle. Am J Psychiatry 1974;131:827–9.
7. Lieber AL, Sherin CR. Homicides and the lunar cycle: toward a
theory of lunar inuence on human emotional disturbance. Am J
Psychiatry 1972;129:69–74.
8. Lieber AL. On the moon again. Am J Psychiatry 1975;132:669–70.
9. Lester D. Temporal variation in suicide and homicide. Am J Epidemiol
1979;109:517–20.
10. Alonso Y. Geophysical variables and behavior: LXXII. Barometric
pressure, lunar cycle, and trafc accidents. Percept Mot Skills
1993;77:371–6.
11. Voracek M, Loibl LM, Kapusta ND, et al. Not carried away by a
moonlight shadow: no evidence for associations between suicide
occurrence and lunar phase among more than 65,000 suicide cases
in Austria, 1970-2006. Wien Klin Wochenschr 2008;120:343–9.
12. Owen C, Tarantello C, Jones M, et al. Lunar cycles and violent
behaviour. Aust N Z J Psychiatry 1998;32:496–9.
13. Bevington M. Lunar biological effects and the magnetosphere.
Pathophysiology 2015;22:211–22.
14. Culver R, Rotton J, Kelly IW. Geophysical variables and behavior:
Xlix. Moon mechanisms and myths: A critical appraisal of
explanations of purported lunar effects on human behavior. Psychol
Rep 1988;62:683–710.
15. Lynch R. Letter: Comments on "homicides and the lunar cycle". Am
J Psychiatry 1974;131:230.
16. Coates W, Jehle D, Cottington E. Trauma and the full moon: a waning
theory. Ann Emerg Med 1989;18:763–5.
17. Calver LA, Stokes BJ, Isbister GK. The dark side of the moon. Med J
Aust 2009;191:692˗4.
18. Vance DE. Belief in lunar effects on human behavior. Psychol Rep
1995;76:32–4.
19. Rotton J, Kelly IW. Much ado about the full moon: A meta-analysis of
lunar-lunacy research. Psychol Bull 1985;97:286–306.
20. Campbell DE, Beets JL. Lunacy and the moon. Psychol Bull
1978;85:1123–9.
21. Margot JL. No evidence of purported lunar effect on hospital
admission rates or birth rates. Nurs Res 2015;64:168–75.
22. Martin SJ, Kelly IW, Saklofske DH. Suicide and lunar cycles: a critical
review over 28 years. Psychol Rep 1992;71:787–95.
on 15 January 2019 by guest. Protected by copyright.http://bmjopen.bmj.com/BMJ Open: first published as 10.1136/bmjopen-2018-022759 on 15 January 2019. Downloaded from
8NäyhäS. BMJ Open 2019;9:e022759. doi:10.1136/bmjopen-2018-022759
Open access
23. Rotton J, Kelly IW, Frey J. Geophysical variables and behavior: X.
Detecting lunar periodicities: something old, new, borrowed, and
true. Psychol Rep 1983;52:111–6.
24. Walters E, Markley RP, Tiffany DW. Lunacy: a type I error? J Abnorm
Psychol 1975;84:715–7.
25. Chapman S, Morrell S. Barking mad? another lunatic hypothesis
bites the dust. BMJ 2000;321:1561–3.
26. Stomp W, Fidler V, ten Duis HJ, et al. Relation of the weather and the
lunar cycle with the incidence of trauma in the Groningen region over
a 36-year period. J Trauma 2009;67:1103–8.
27. Tasso J, Miller E. The effects of the full moon on human behavior. J
Psychol 1976;93:81–3.
28. Gupta M, Kumar M. Lunar cycle affecting homicidal death in Varanasi
region: a reality or myth. Int J Sci Res 2015;4:1773˗5.
29. Garzino SJ. Lunar effects on mental behavior. A defense of the
empirical research. Environ Behav 1982;14:395˗417.
30. Thakur CP, Sharma D. Full moon and crime. Br Med J
1984;289:1789–91.
31. Oderda GM, Klein-Schwartz W. Lunar cycle and poison center calls.
J Toxicol Clin Toxicol 1983;20:487–95.
32. de Castro JM, Pearcey SM. Lunar rhythms of the meal and alcohol
intake of humans. Physiol Behav 1995;57:439–44.
33. Henkirikoskatsaus LM. Katsauksia 10/2016. [Homicide Survey 2016,
in Finnish] Institute of Criminology and Legal Policy: University of
Helsinki, 2016. https:// helda. helsinki. / bitstream/ handle/ 10138/
160000/ Katsauksia_ 10_ Lehti_ 2016. pdf.
34. Ciacopassi DJ, Sparger JR. The effects of emergency medical care
on the homicide rate: some additional evidence. J Crim Justice
1992;20:249˗59.
35. Cros J, Alvarez JC, Sbidian E, et al. Survival time estimation using
Injury Severity Score (ISS) in homicide cases. Forensic Sci Int
2013;233:99–103.
36. Templer DI, Veleber DM, Brooner RK. Geophysical variables and
behavior: VI. Lunar phase and accident injuries: a difference between
night and day. Percept Mot Skills 1982;55:280–2.
37. Näyhä S. Short and medium-term variations in mortality in Finland.
A study on cyclic variations, annual and weekly periods and certain
irregular changes in mortality in Finland during the period 1868˗1972.
Scand J Soc Med 1981:1–101.
38. Tiihonen J, Räsänen P, Hakko H. Seasonal variation in the occurrence
of homicide in Finland. Am J Psychiatry 1997;154:1711–4.
39. Wahlsten P, Koiranen V, Saukko P. Survey of medicolegal
investigation of homicides in the city of Turku, Finland. J Clin
Forensic Med 2007;14:243–52.
40. Holzheimer RG, Nitz C, Gresser U. Lunar phase does not inuence
surgical quality. Eur J Med Res 2003;8:414˗8.
41. Prugh LR, Golden CD. Does moonlight increase predation risk?
Meta-analysis reveals divergent responses of nocturnal mammals to
lunar cycles. J Anim Ecol 2014;83:504–14.
on 15 January 2019 by guest. Protected by copyright.http://bmjopen.bmj.com/BMJ Open: first published as 10.1136/bmjopen-2018-022759 on 15 January 2019. Downloaded from
... With regard to homicides in Finland it has recently been shown that contrary to most of the earlier assumptions during full moon 15% fewer homicides were committed than during the new moon phase [19]. This result held true for all seasons, weekdays, genders and ages. ...
... The close similarity of the synodic lunar with the menstrual cycle comes to mind and although, as with the lunar effect on suicides, contradictory results have been published in connection with lunar and menstrual periodicities, the lengths of the two cycles are too similar to be ignored. Yet, the few studies in which female suicides, but not those of males, were shown to exhibit some relationship to the phase of the moon did not show any coherent trend: a statistically significant lunar periodicity of self-inflicted poisoning in Winnipeg (Canada) has been reported to be greatest for women during the first quarter of the lunar cycle [28], while Kmetty et al. [19] reported fewer suicides on the day of full moon than could be expected, but only for post-menopausal females aged 50-59 years. The latter result agrees with our suicide finding (this paper) and also some earlier reports that older, post-menopausal women were less affected by season-bound depressive symptoms [38,42]. ...
... Geomagnetic storms can trigger strokes [53], and a significantly higher rate of suicides by females but not males during times of geomagnetic storms has been reported [54], in contrast to a finding of a decrease (but in a considerably Ref ( narrower age-group) [29]. For a study on the cosmogeophysical effects in the Arctic, unfortunately involving only male subjects (12 men aged [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38], the conclusion was that despite wide individual differences emotional states were clearly subject to central and autonomous nervous system and humoral effects "modulated…by the cosmogeophysical and meteorological agents" [55]. Pre-and post-menopausal women differ with regard to the menstrual period, which is "a carefully orchestrated sequence of interactions among the hypothalamus, pituitary, ovary, and endometrium" [56]. ...
Article
Full-text available
Suicide data for this study were available for the period of March 1988 to June 2011, and involved 2111 male and 494 female victims from the Finnish province of Oulu. Data for lunar phases during that period were categorised into three groups: new moon (<25% visible), full moon (>75% visible) and other times with values in between. Seasonal effects were controlled with definitions for winter (Nov, Dec, Jan), spring (Feb, Mar, Apr), summer (May, June, July), and autumn (Aug, Sep, Oct). Suicide occurrences during different lunar phases were compared with their expected distribution using multinomial tests with all tests being two-tailed. Statistical significance was set at p < 0.05. No correlation between suicides and moon phase in any of the four seasons was apparent for male victims, but in winter for women it was (p = 0.001). Further analysis of the data revealed that the full moon association was statistically significant only for premenopausal women, defined as female victims younger than 45 years of age. To explain this unexpected finding a number of factors were considered, e.g., the darkness of a northern Finnish winter with increases of SAD and depression especially in premenopausal women, the influence of the lunar periodicity on the menstrual cycle, and cosmogeophysical effects on the humoral and autonomous nervous system.
... Lunar phases are well known to affect reproductive and other behaviours in animals, but were dismissed for years in connection with humans until Wehr [4] could recently show that synchrony of sleep-wake and bipolar mood cycles can indeed be related to lunar cycles. Earlier rejected as false, earthquakes have also recently been shown to be associated with lunar phases [5], and contrary to earlier assumptions, homicides (at least in Finland) were now found to be moonphase correlated [6]. In relation to suicides, to dismiss the studies with positive findings, cited in [7], as "may also be false positives" by Plöderl and Hengartner, assumes that our study was false-positive (for which there is no clear proof on account of the differences in geographic and social setting between other studies as Plöderl and Hengartner themselves admit in the penultimate sentence of their Commentary). ...
Article
Background: Trauma patterns in adults are influenced by weather conditions, lunar phases, and time of year. The extent to which these factors contribute to pediatric trauma is unclear. Objective: The present study aimed to review patients from a single Level I pediatric trauma center to determine the influence of weather, the lunar cycle, and time of year on trauma activity. Methods: A retrospective review of trauma activations (n = 1,932) was conducted from 2015 to 2017. Injury type and general demographics were collected. Weather data and lunar cycles were derived from historical databases. Results: Days with no precipitation increased the total number of injuries of all types compared with those with precipitation (p < .001). Blunt and penetrating injuries were more likely to occur during full moons, whereas burn injuries were significantly higher during new moons (p < .001). Blunt trauma was significantly higher in September than all other months, F(11, 1,921) = 4.25, p < .001, whereas January had a significantly higher number of burns than all other months (p < .001). Conclusions: Pediatric trauma trends associated with external factors such as weather, lunar cycles, and time of year can inform hospital staffing decisions in anticipation of likely injuries and help direct injury prevention efforts.
Article
Full-text available
Визначено вплив абіотичних чинників середовища на функціональне здоров’я жінок різних вікових груп. З’ясовано, що основним регуляторним механізмом живого організму, який забезпечує гомеостаз, є вегетативна нервова система. За зміни внутрішнього і зовнішнього середовища за допомогою вегетативно-гуморальних механізмів відбувається регуляція функціональних (фізіологічних і патологічних) коливальних процесів в основних системах органів, визначаючи ступінь пристосувальної реакції організму до впливу цих чинників. Дослідження стану вегетативної нервової системи людини є першочерговим завданням в умовах пристосування фізіологічних і функціональних систем організму до умов життєдіяльності, в т.ч. за дії на організм патологічних чинників. Відомо, що оцінка функціонування вегетативної нервової системи може бути фізіологічним маркером виявлення механізмів індивідуальної мінливості і реагування на чинники середовища. Викладено результати досліджень впливу деяких абіотичних чинників, а саме фаз Місяця, на вегетативний баланс організму людини, співвідношення активності симпатичної нервової системи до парасимпатичної нервової системи та функціональне здоров’я жінок різних вікових груп. Встановлено, що вплив такого абіотичного чинника, як зміна фаз Місяця на організм призводить до достовірних змін функціональної активності і гомеостазу організму. Показники фаз місячної активності функціональних систем, дублюючи лінію норми, мають однакову спрямованість, вони відрізняються амплітудою, формують вікові особливості тонусу вегетативної нервової системи та стану функціонального здоров’я у жінок різних вікових груп. Ключові слова: середовище, чинник, здоров’я, гомеостаз, вегетативний баланс.
Article
The current study considers the data on road traffic accidents in order to see the influence of the moon on the driver behaviour by way of its position and illumination. The analysis was based on the visual tools widely used for time series data in time and frequency domains. The present study could not detect any influence of the moon on the traffic accidents. This study does not see a reason for this result not being valid for the human behaviours underpinning similar data. Key Words: Human Tidal Wave Theory, Moon Phase, Position of the Moon, Supermoon, Road Traffic Accidents, Human Behaviour, Time Series Analysis, Frequency Domain Analysis
Article
Full-text available
Background: It is commonly believed that a full moon affects human behavior or the occurrence and outcome of various diseases; thus, the occurrence of out-of-hospital cardiac arrest (OHCA) might increase during full moon nights. Methods and Results: This nationwide, population-based observational study consecutively enrolled OHCA patients in Japan with attempted resuscitation between 2005 and 2016. The primary outcome measure was the occurrence of OHCA. Based on the doublecontrol method, assuming Poisson sampling, we evaluated the average number of OHCA events that occurred on full moon nights compared with that which occurred on control nights, which included events that occurred on the same calendar days 1 week before and after the full moon nights. A total of 29,552 OHCA that occurred on 148 full moon nights and 58,707 OHCA that occurred on 296 control nights were eligible for analysis. The occurrence of OHCA did not differ between full moon and control nights (199.7 vs. 198.3 per night; relative risk [RR], 1.007; 95% CI: 0.993–1.021). On subgroup analysis, compared with control nights, the RR of OHCA occurrence were 1.013 (95% CI: 0.994–1.032, P=0.166) and 0.998 (95% CI: 0.977–1.020, P=0.866) for cardiac and non-cardiac origins, respectively. Conclusions: In this population, there was no significant difference in OHCA occurrence between full moon and control nights.
Article
Full-text available
In this study of all of the violent deaths in the US over two years, clear monthly and daily variations were found. Suicide peaked in the Spring and Fall; homicide in July and December. Suicide was more common on Mondays; homicide on Saturdays and Sundays. Homicide was more common on national holidays, while suicide tended to be less common. No lunar variation was found. PIP The author analyzes monthly and daily variations in the incidence of suicide and homicide in the United States over a two-year period.
Article
Full-text available
Summary.-In this paper the explanations put forward by lunar advocates to account for a "lunar effect" on human behavior are critically appraised. The hypotheses considered are ozone, moonlight, gravity, tidal force, geo- magnetism, electromagnetism, weather, ions, and ELF waves. It is concluded that none of these are sufficient to explain the alleged effects of the moon on human behavior. In view of (a) the lack of a satisfactory mechanism, (b) the lack of a reliable connection between lunar periodicities and human behavior, and (c) the generally negative results obtained in studies, it is suggested that the scientific community exercise great caution with regard to further studies claiming lunar effects on human behavior. Interest
Article
Full-text available
Studies indicate that a fraction of nursing professionals believe in a "lunar effect"-a purported correlation between the phases of the Earth's moon and human affairs, such as birth rates, blood loss, or fertility. This article addresses some of the methodological errors and cognitive biases that can explain the human tendency of perceiving a lunar effect where there is none. This article reviews basic standards of evidence and, using an example from the published literature, illustrates how disregarding these standards can lead to erroneous conclusions. Román, Soriano, Fuentes, Gálvez, and Fernández (2004) suggested that the number of hospital admissions related to gastrointestinal bleeding was somehow influenced by the phases of the Earth's moon. Specifically, the authors claimed that the rate of hospital admissions to their bleeding unit is higher during the full moon than at other times. Their report contains a number of methodological and statistical flaws that invalidate their conclusions. Reanalysis of their data with proper procedures shows no evidence that the full moon influences the rate of hospital admissions, a result that is consistent with numerous peer-reviewed studies and meta-analyses. A review of the literature shows that birth rates are also uncorrelated to lunar phases. Data collection and analysis shortcomings, as well as powerful cognitive biases, can lead to erroneous conclusions about the purported lunar effect on human affairs. Adherence to basic standards of evidence can help assess the validity of questionable beliefs.This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License, where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially.
Article
The debate about how far the Moon causes biological effects has continued for two millennia. Pliny the Elder argued for lunar power "penetrating all things", including plants, fish, animals and humans. He also linked the Moon with tides, confirmed mathematically by Newton. A review of modern studies of biological effects, especially from plants and animals, confirms the pervasive nature of this lunar force. However calculations from physics and other arguments refute the supposed mechanisms of gravity and light. Recent space exploration allows a new approach with evidence of electromagnetic fields associated with the Earth's magnetotail at full moon during the night, and similar, but more limited, effects from the Moon's wake on the magnetosphere at new moon during the day. The disturbance of the magnetotail is perhaps shown by measurements of electric fields of up to 16V/m compared with the usual <1V/m, suggesting the possibility of weak biological effects on some sensitive organisms. Similar intensities found in sferics, geomagnetic storms, aurora disturbance, sensations of a 'presence' and pre-seismic electromagnetic radiation are known to affect animals and 10-20% of the human population. There is now evidence for mechanisms such as calcium flux, melatonin disruption, magnetite and cryptochromes. Both environmental and receptor variations explain confounding factors and inconsistencies in the evidence. Electromagnetic effects might also account for some evolutionary changes. Further research on lunar biological effects, such as acute myocardial infarction, could help the development of strategies to reduce adverse effects for people sensitive to geomagnetic disturbance.
Article
Data were gathered in a large metropolitan area over a period of one year as to nine categories of 34,318 criminal offenses committed during the phases of the full moon and non full moon. It was found that the eight categories of rape, robbery and assault, burglary, larceny and theft, auto theft, offenses against family and children, drunkenness, and disorderly conduct occurred significantly more frequently during the full moon phase than at other times of the year. Only the category of homicide did not occur more frequently during the full moon phase. The results support further exploration and research related to cosmic influences on man's behavior.
Article
The risk of predation strongly affects mammalian population dynamics and community interactions. Bright moonlight is widely believed to increase predation risk for nocturnal mammals by increasing the ability of predators to detect prey, but the potential for moonlight to increase detection of predators and the foraging efficiency of prey has largely been ignored. Studies have reported highly variable responses to moonlight among species, calling into question the assumption that moonlight increases risk. Here, we conducted a quantitative meta-analysis examining the effects of moonlight on the activity of 59 nocturnal mammal species to test the assumption that moonlight increases predation risk. We examined patterns of lunarphilia and lunarphobia across species in relation to factors such as trophic level, habitat cover preference, and visual acuity. Across all species included in the meta-analysis, moonlight suppressed activity. The magnitude of suppression was similar to the presence of a predator in experimental studies of foraging rodents (13.6% and 18.7% suppression, respectively). Contrary to the expectation that moonlight increases predation risk for all prey species, however, moonlight effects were not clearly related to trophic level and were better explained by phylogenetic relatedness, visual acuity, and habitat cover. Moonlight increased the activity of prey species that use vision as their primary sensory system and suppressed the activity of species that primarily use other senses (e.g., olfaction, echolocation), and suppression was strongest in open habitat types. Strong taxonomic patterns underlay these relationships: moonlight tended to increase primate activity, whereas it tended to suppress the activity of rodents, lagomorphs, bats, and carnivores. These results indicate that visual acuity and habitat cover jointly moderate the effect of moonlight on predation risk, whereas trophic position has little effect. While the net effect of moonlight appears to increase predation risk for most nocturnal mammals, our results highlight the importance of sensory systems and phylogenetic history in determining the level of risk. This article is protected by copyright. All rights reserved.
Article
Objective: It is commonly believed that the full moon exerts an influence on violence and aggression in psychiatric settings. The literature to date is contentious. This study used a robust methodology to examine the hypothesis that there was an increased frequency of violent and aggressive behaviour among hospitalised psychiatric clients at the time of the full moon. Method: Prospective data were collected in five inpatient psychiatric settings across the Northern Sydney Area Health Service. Morrison’s hierarchy of violence and aggression was used to rate behaviour. Lunar phases were clearly defined and Poisson regression used to examine relationships between lunar phase and violence. Extraneous temporal variation was considered. Results: No significant relationship was found between total violence and aggression or level of violence and aggression and any phase of the moon. Conclusion: Future research could profitably examine the implications of a belief in the lunar effect among health workers in the face of evidence that no relationship exists between violence, aggression and the lunar cycle.