Association between affective temperaments and season of birth in a general student population.

Abstract

Several studies indicate a significant association between birth season and personality and neuropsychiatric disorders. The aim of our present study was to investigate the association between affective temperaments and season of birth in a nonclinical sample.
366 university students completed the standardized Hungarian version of the Temperament Evaluation of Memphis, Pisa, Paris and San Diego-Auto-questionnaire (TEMPS-A). Ordinary Least Squares regression was applied to explain the relationship between TEMPS-A subscale and birth season of the respondents.
We found a significant association between temperament scores and birth season in the case of the Hyperthymic, Cyclothymic, Irritable and Depressive temperaments, while no significant results emerged for the Anxious temperament.
The relatively small sample size, especially in the case of seasonal and monthly subsamples limits generalization of our results.
Our results support the evidence that there is a strong association between season of birth and personality, extending the results to affective temperaments as well. Furthermore, our results are in line with clinical observations concerning the seasonal variation of onset and hospitalization due to affective episodes. This is especially important, since affective temperaments are conceived as the subaffective and subclinical manifestations of major and minor affective disorders indicating a risk for the development of these disorders and also exerting a possible pathoplastic effect, thus our results also have clinical significance.

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Research report
Association between affective temperaments and season of birth in a general
student population
Zoltan Rihmera,⁎, Peter Erdosb, Mihaly Ormosb, Konstantinos N. Fountoulakisc,
Gustavo Vazquezd, Maurizio Pompilie,f,g, Xenia Gondaa,h
aDepartment of Clinical and Theoretical Mental Health, Kutvolgyi Clinical Center, Semmelweis University; Kutvolgyi ut 4., 1125 Budapest, Hungary
bDepartment of Finance, Budapest University of Technology and Economics; Muegyetem rakpart 9, 1111 Budapest, Hungary
c3rd Department of Psychiatry, Aristotle University, University Hospital AHEPA, 1 Kyriakidi Str, 54636 Thessaloniki, Greece
dDepartment of Neuroscience, University of Palermo; Mario Bravo 1259, C.P. 1425. Buenos Aires, Argentina
eDepartment of Neuroscience, Mental Health and Sensory Function - Suicide Prevention Center, Sant'Andrea Hospital, Sapienza University or Rome,
Via di Grottarossa, 1035, 00189 Rome, Italy
fMcLean Hospital, Harvard Medical School, 115 Mill Street , Belmont, MA 02478, USA
gVilla Rosa Research Center, Italy
hDepartment of Pharmacology and Pharmacotherapy, Semmelweis University; Nagyvarad ter 4., 1084 Budapest, Hungary
a r t i c l ei n f o a b s t r a c t
Article history:
Received 14 December 2010
Received in revised form 25 January 2011
Accepted 25 January 2011
Available online 21 February 2011
Background: Several studies indicate a significant association between birth season and
personality and neuropsychiatric disorders. The aim of our present study was to investigate the
association between affective temperaments and season of birth in a nonclinical sample.
Methods: 366 university students completed the standardized Hungarian version of the
Temperament Evaluation of Memphis, Pisa, Paris and San Diego-Auto-questionnaire (TEMPS-A).
Ordinary Least Squares regression was applied to explain the relationship between TEMPS-A
subscale and birth season of the respondents.
Results: We found a significant association between temperament scores and birth season in
the case of the Hyperthymic, Cyclothymic, Irritable and Depressive temperaments, while no
significant results emerged for the Anxious temperament.
Limitations: The relatively small sample size, especially in the case of seasonal and monthly
subsamples limits generalization of our results.
Conclusions: Our results support the evidence that there is a strong association between season
of birth and personality, extending the results to affective temperaments as well. Furthermore,
our results are in line with clinical observations concerning the seasonal variation of onset and
hospitalization due to affective episodes. This is especially important, since affective
temperaments are conceived as the subaffective and subclinical manifestations of major and
minor affective disorders indicating a risk for the development of these disorders and also
exerting a possible pathoplastic effect, thus our results also have clinical significance.
© 2011 Elsevier B.V. All rights reserved.
Keywords:
Affective temperaments
Birth season
Personality
Seasonality
TEMPS-A
1. Introduction
Periodicity, cyclicity, and annual rhythms (including sea-
sonality) that are inherent characteristics of living organisms
have been reported for diverse physiological and pathological
conditions and phenomena. Season of birth has been consid-
ered to be an important element in determining personality
and illness already in the pre-scientific medical era and this
tradition lives on in several contemporary concepts ranging
from astrological beliefs to science (Fountoulakis et al., 2007).
Several studies indicate a significanteffectof season of birthon
personality traits and characteristics (Gupta, 1992; Chotai and
Wiseman, 2005; Tochigi et al., 2004), handedness (Martin and
Jones, 1999), suicide (Salib and Cortina-Borja, 2006; Chotai
Journal of Affective Disorders 132 (2011) 64–70
⁎ Corresponding author at: Semmelweis University, Faculty of Medicine,
KutvolgyiClinicalCenter,1125BudapestKútvölgyiút4,Hungary.Tel./fax:+36
1 355 8498.
E-mail address: rihmerz@kut.sote.hu (Z. Rihmer).
0165-0327/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jad.2011.01.015
Contents lists available at ScienceDirect
Journal of Affective Disorders
journal homepage: www.elsevier.com/locate/jad

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et al.,1999; Dome etal.,2010), intelligence(Bibby etal.,1996),
neuropsychiatric disorders (Torrey et al., 2000) such as
schizophrenia (Davies et al., 2003; Torrey et al., 1997;
Castrogiovanni et al., 1998; Mino and Oshima, 2006), major
depression (Mino et al., 2000), bipolar disorder (Torrey et al.,
1997; Mino et al., 2000), epilepsy (Procopio and Marriott, 1998;
Procopio et al., 2006) and brain tumors (Brenner et al., 2004).
Seasonofbirthisofpeculiarinterestwhenstudyingtheeffectof
environment in the development of several psychological and
psychiatric phenomena, since it can be considered an unspecific
environmental factor which is associated with a complex
pattern of varying environmental influences especially in high
latitudes,suchastemperature, photoperiod,and consequential-
ly behavioral rhythms, nutrition, infections, stress and lifestyle
(Chotai et al., 2009; Chotai and Wiseman, 2005). Therefore the
possible mediating factors of birth season are complex and
largely still unknown. Several specific phenomena related to
seasons have been suggested as possible underlying factors,
which may influence neurodevelopment, and consequentially
the development of personality and psychiatric disorders as
well. These factors include photoperiod, ambient temperature,
weather, nutritional deficiencies, infections, toxins, maternal
hormones, as well as pregnancy and birth complications
(Kamata et al., 2009; Torrey et al., 1997; Gortmaker et al.,
1997;Nataleetal.,2007;NataleandAdan,1999).Seasonofbirth
can be considered a complex indicator of environmental
influences during season of conception, gestation, delivery and
early postnatal life (Chotai et al., 2002). Because of this complex
constellationofphenomenavaryingwithseason,eveninspiteof
some strong associations reported between season of birth and
several factors, we still do not understand the specific
mechanisms underlying this association.
Season of birth was also associated with central mono-
amine and monoamine metabolite levels in several studies
(Chotai and Adolfsson, 2002; Chotai and Asberg, 1999; Chotai
et al., 2006) and there may also be an association between
season of birth and dynamics of the turnover of monoamines
and season of birth and interactions between monoaminergic
systems (Brenner et al., 2004). Seasonally varying mono-
amine levels and the association between monoamine
turnover and birth season are suspected in part to play a
role in the background of association of certain personality
traits with season of birth, since several well-known and
validated personality traits have been associated with
monoamine functions (Cloninger et al., 1993). In earlier
studies Neuroticism, Impulsivity and Venturesomeness were
associated with season of birth (Gupta, 1992) and recently
several studies consistently point to an association between
season of birth and novelty seeking and reward dependence
(Chotai et al., 2002, 2009). However, other personality traits
and temperaments, such as Akiskal's affective temperaments
have not so far been studied with respect to their association
with birth season. Akiskal developed his framework of
affective temperaments building on ancient traditions con-
ceptualizing personality based on the association of body
humors and emotional reactivity (Akiskal and Akiskal, 2007;
Pompili et al., 2008a), and extrapolated these theoretical
considerations and observations of patients and their healthy
relatives to describe five affective temperaments (Depressive,
Cyclothymic, Anxious, Hyperthymic and Irritable), and also
developed a self-report questionnaire to measure affective
temperaments in the general population (Akiskal et al.,
2005). In this conceptual model, affective temperaments are
considered the subaffective, subclinical manifestation of
affective disorders, also conferring an increased risk towards
the manifestation of minor and major mood disorders
(Akiskal and Akiskal, 2007; Akiskal et al., 2005) and suicidal
behavior (Pompili et al., 2008b; Rihmer et al., 2009; Vazquez
et al., 2010).
The aim of our present study was to investigate the
possible association between affective temperaments and
season of birth in a nonclinical sample.
2. Methods
2.1. Study subjects
366 university students (mean age 20.59 years, SD:
1.96 years, range: 18–35 years) of Budapest University of
Technology and Economics (BUTE) completed the standard-
ized Hungarian version of the Temperament Evaluation of
Memphis, Pisa, Paris and San Diego-Auto-questionnaire
(TEMPS-A) (Rozsa et al., 2008). This scale is different from
most other temperament scales in that it taps subaffective
trait expressions as they were conceptualized in Greek
psychological medicine and, in more recent times, German
psychiatry. While the first version of TEMPS-A contained 84
items (Akiskal and Akiskal, 2005), later, clinical and theoret-
ical considerations led to the addition of 26 new items
describing the Anxious temperament, resulting in the current
110-item-long version of the TEMPS-A (Akiskal and Akiskal,
2005; Akiskal et al., 2005).
Among the participants there were 258 males (mean age:
20.87 years, SD: 2.08 years, range: 19–35 years) and 108
females (mean age: 19.92 years, SD: 1.41 years, range: 18–
25 years). All respondents attended the “Principles of Invest-
ment Theory” course at the university. Participation in the
study was voluntary, and a 5% extra credit was offered as a
compensation.
The investigation was carried out in accordance with the
latest version of the Declaration of Helsinki. The study has
been approved by the Scientific and Research Ethics Commit-
tee of Scientific Health Council in charge of experimentation
with human subjects. All subjects were given thorough
explanation oftheproceduresofthestudyandallparticipants
gave informed consent before participating in the study.
2.2. Statistics
OLS (Ordinary Least Squares) regression was applied to
explain therelationship between TEMPS-A subscale scores and
age,sexandbirthseasonoftherespondents.Wedidnotcontrol
for the distribution of variables. Consistent standard errors
were estimated using White (1980) consistent covariance
matrix estimation. We compiled 11 dummy variables for the
month of birth from February to December and three other for
the season of birth from spring to autumn; that is, we used
January and winter as a point of reference. Seasons were
defined according to the astronomical definition as follows:
winter is from December 22 to March 20, spring is from March
21 to June 20, summer is from June 21 to September 22 and
autumn is from September 23 to December 21.
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3. Results
Descriptive statistics of the subscale scores by gender are
shown in Table 1. Scores are shown as the total subscale score
divided by the number of items answered yielding a score
between 0 and 1.
We found a significant gender difference in the case of all
five TEMPS-A subscales. Women scored significantly higher
in case of the Anxious, Cyclothymic and Depressive subscales
(t=4.8420, p=0.0000; t=2.9809, p=0.0031; t=3.4050,
p=0.0007, respectively), while men had significantly higher
score on the Hyperthymic and Irritable subscales (t=2.7700,
p=0.0059; t=1.9802, p=0.484, respectively) (Table 1). We
computed the mean score of each subscales in each month
andfor all four seasonsseparately(Table 2). Birth monthsand
birth seasons show a uniform distribution in the total sample
and also in the gender subsamples, however, the standard
deviations of the gender subsamples are high.
We regressed each temperament subscale on birth month
dummies, the gender dummy and age applying OLS (Table 3).
The results indicated the same significant association between
gender and temperament subscale scores as the t-tests above.
Furthermore, the score on the Cyclothymic subscale signifi-
cantly declines with age (β=−0.0112, p=0.0114), while in
the case of the Depressive temperament it significantly
increases with age (β=0.0068, p=0.0338) (Table 3).
OLS estimates show that there is a significant relationship
between the five temperament scores and birth month
controlling for gender and age (Table 3).
In the case of the Hyperthymic temperament, regression
results indicate a significantassociation between scores on this
temperament scale and birth month: individuals born during
the period between April–June and October–November score
significantly higher compared to those born in January (April:
β=0.1029, p=0.0387; May: β=0.1307, p=0.0014; June:
β=0.1124, p=0.0036; October: β=0.1153, p=0.0057; No-
vember: β=0.0954, p=0.0327). The September dummy has
the lowestestimated parameter, indicatingthe lowestscore on
the Hyperthymic temperament scale for those born in
(β=0.0474, p=0.2352); although this result was not signif-
icant (Table 3).
In the case of the Cyclothymic temperament, only the
coefficient for July was significant, indicating that the scores
on the Cyclothymic temperament scale are highest in those
born in July (β=0.1066, p=0.0123). The Cyclothymic
temperament showed the lowest score among those who
were born in November (β=−0.0248, p=0.5715); however,
this result is not significant (see Table 3).
In the case of the Irritable temperament, OLS regression
results showed that this temperament has significantly
higher scores in the period between April and December
than in January: the probability of occurrence is approxi-
mately constant between April and June and soars in July,
then in the remaining part of the year it has no definite
direction (April: β=0.1047, p=0.0122, 0.1034, p=0.0364;
May: β=0.0882, p=0.222; June: β=0.0905, p=0.0176;
July: β=0.1586, p=0.0001; August: β=0.1047, p=0.0122,
September: β=0.1262, p=0.0026, October: β=0.1079,
Table 1
Descriptive statistics: Mean TEMPS-A scores (SD) by subscales and gender.
TEMPS-A subscales N itemsTotalMales Femalestp
Mean St. devMeanSt. devMeanSt. dev
Anxious
Cyclothymic
Depressive
Hyperthymic
Irritable
26
21
21
21
20 or 21a
0.1961
0.3499
0.2814
0.5863
0.3137
0.1636
0.1712
0.1280
0.1782
0.1671
0.1701
0.3328
0.2669
0.6028
0.3248
0.1552
0.1648
0.1261
0.1757
0.1705
0.2582
0.3907
0.3161
0.5467
0.2870
0.1670
0.1800
0.1265
0.1787
0.1562
4.8420
2.9809
3.4050
2.7700
1.9802
b0.0001
0.0031
0.0007
0.0059
0.0484
aMales answer 20 items on the Irritable subscale and females answer 21 items.
Table 2
Number of respondents by gender and the means of TEMPS-A subscale scores by season of birth.
Birth month/seasonMale (%) Female (%)Total (%)Anxious CyclothymicDepressive HyperthymicIrritable
January
February
March
April
May
June
July
August
September
October
November
December
Spring
Summer
Autumn
Winter
25 (9.69%)
11 (4.26%)
20 (7.75%)
14 (5.43%)
25 (9.69%)
27 (10.47%)
18 (6.98%)
30 (11.63%)
24 (9.30%)
23 (8.92%)
17 (6.59%)
24 (9.30%)
59 (22.87%)
74 (28.86%)
60 (23.26%)
64 (24.81%)
7 (6.48%)
11 (10.19%)
7 (6.48%)
9 (8.33%)
11 (10.19%)
9 (8.33%)
15 (13.89%)
4 (3.70%)
7 (6.48%)
10 (9.26%)
13 (12.04)
5 (4.63%)
31 (28.70%)
26(24.07%)
28 (25.93%)
24 (22.22%)
32 (8.74%)
22 (6.01%)
27 (7.38%)
23 (6.28%)
36 (9.84%)
36 (9.84%)
33 (9.02%)
34 (9.29%)
31 (8.47%)
33 (9.02%)
30 (8.20%)
29 (7.92%)
90 (24.59%)
100 (27.32%)
88 (24.04%)
88 (24.04%)
0.1995
0.2080
0.1980
0.2358
0.1699
0.2179
0.2937
0.1719
0.1526
0.1807
0.1641
0.1698
0.2162
0.2035
0.1726
0.1906
0.3155
0.3377
0.3739
0.3644
0.3214
0.3466
0.4372
0.3403
0.3917
0.3449
0.3095
0.3169
0.3455
0.3805
0.3425
0.3268
0.2887
0.2792
0.3157
0.3188
0.2394
0.2712
0.3434
0.2773
0.2873
0.2367
0.2730
0.2660
0.2804
0.2976
0.2500
0.2955
0.5089
0.5823
0.5697
0.6046
0.6349
0.6217
0.5455
0.5910
0.5576
0.6190
0.5937
0.5977
0.6148
0.5710
0.6136
0.5471
0.2196
0.2423
0.2907
0.3200
0.3048
0.3118
0.3693
0.3309
0.3478
0.3238
0.3452
0.3371
0.3134
0.3484
0.3364
0.2518
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p=0.0014, November: β=0.1316, p=0.0024, December:
β=0.1129, p=0.0053) (Table 3).
For the Depressive temperament, OLS results indicated
that Depressive temperament score is lowest in those born in
May (β=−0.0525, p=0.0687) and October (β=−0.0563,
p=0.0618), and although these results were not significant,
they showed a strong tendency. Depressive temperament
score was highest in those born in July (β=0.0448,
p=0.1945), but this result was also not significant (Table 3).
In the case of the Anxious temperament as explained by
month of birth controlled for age and gender none of the
coefficients were significant. Although not significant, the
Anxioustemperament showedthehighest score amongthose
born in July (β=0.0756, p=0.1329), while the Anxious
temperament score was lowest in those born in November
(β=−0.050, p=0.2312) (Table 3).
Investigating the association between temperament scores
and season of birth controlling for age and gender, we found no
significant results for the Anxious temperament. In the case of
the Cyclothymic temperament, OLS regression indicated that
this temperament has significantly higher scores in those born
during summer compared to winter borns (β=0.0505,
p=0.0345). For the Depressive temperament, OLS regression
indicatedsignificantlylowerscoresinthosebornduringautumn
compared to winter borns (β=−0.0447, p=0.0138).
Hyperthymic temperament had significantly higher scores in
spring and autumn borns compared to winter borns
(β=0.0706, p=0.0068; β=0.0680, p=0.0138). Concerning
the Irritable temperament, the results indicate that this
temperament has significantly lower scores in those born in
winter compared to subjects born in all other seasons (spring:
β=0.0618, p=0.0112; summer: β=0.0398, p=0.0001; au-
tumn: β=0.0840, p=0.0003) (Table 4, Fig. 1).
Considering the results significant at pb0.05, for those
born in spring the most likely temperament is Hyperthymic
and Irritable, for summer borns Cyclothymic and Irritable, in
autumn borns the Depressive temperament is the least likely,
while Hyperthymic and Irritable are the most likely, while in
winter borns the Irritable temperament is the least likely.
4. Discussion
In our study we found a significant association between
the season of birth and four of the five affective tempera-
ments as described by Akiskal (Akiskal and Akiskal, 2005,
2007). Hyperthymic temperament was most common in
spring and autumn borns. The Cyclothymic temperament
proved to be significantly more common in summer borns
than in winter borns. The Irritable temperament was least
common in winter borns compared to the three other
seasons. The Depressive temperament was the least common
in autumn borns. Only in the case of the Anxious tempera-
ments was there no evidence for association with birth
season or month.
Some very interesting and clinically relevant patterns can
be identified in our results. Considering the two basic
temperaments (Depressive and Hyperthymic), the Depres-
sive temperament is most common in summer and winter
Table 3
Ordinary Least Squares regression of TEMPS-A scales on gender, age and month of birth.
VariableAnxious Cyclothymic DepressiveHyperthymic Irritable
Coeff.p Coeff.p Coeff.p Coeff.p Coeff.p
C
Male
Age
February
March
April
May
June
July
August
September
October
November
December
Adj R²
0.1708
−0.0867
0.0046
−0.0152
−0.0061
0.0261
−0.0362
0.0187
0.0756
−0.0169
−0.0453
−0.0260
−0.0503
−0.0233
0.0743
0.0616
0.0000
0.2520
0.7317
0.8780
0.5562
0.3644
0.6829
0.1329
0.6911
0.2425
0.5337
0.2312
0.5807
0.5848
−0.0458
−0.0112
0.0078
0.0593
0.0294
−0.0004
0.0223
0.1066
0.0250
0.0705
0.0252
−0.0248
−0.0023
0.0462
0.0000
0.0289
0.0114
0.8415
0.1644
0.5396
0.9920
0.5683
0.0123
0.5216
0.0738
0.4837
0.5715
0.9546
0.1873
−0.0533
0.0068
−0.0236
0.0232
0.0280
−0.0525
−0.0147
0.0448
−0.0032
0.0015
−0.0563
−0.0216
−0.0166
0.0590
0.0084
0.0003
0.0338
0.4650
0.5229
0.4573
0.0687
0.6459
0.1945
0.9310
0.9623
0.0618
0.5128
0.6277
0.5325
0.0628
−0.0035
0.0905
0.0641
0.1029
0.1307
0.1124
0.0500
0.0744
0.0474
0.1153
0.0954
0.0840
0.0283
0.0000
0.0026
0.4816
0.0609
0.1815
0.0387
0.0014
0.0036
0.2452
0.0974
0.2352
0.0057
0.0327
0.0756
0.2823
0.0459
−0.0047
0.0350
0.0740
0.1034
0.0882
0.0905
0.1586
0.1047
0.1262
0.1079
0.1316
0.1129
0.0406
0.0007
0.0147
0.2063
0.3650
0.0780
0.0364
0.0222
0.0176
0.0001
0.0122
0.0026
0.0014
0.0024
0.0053
Table 4
Ordinary Least Squares regression of TEMPS-A scales on sex, age and season of birth.
VariableAnxious CyclothymicDepressive HyperthymicIrritable
Coeff.p Coeff.pCoeff.pCoeff.pCoeff. p
C
Male
Age
Spring
Summer
Autumn
Adj R²
0.1570
–0.0925
0.0048
0.0222
0.0170
−0.0194
0.0602
0.0650
b0.0001
0.2309
0.3378
0.4632
0.3813
0.5784
–0.0513
−0.0102
0.0083
0.0505
0.0076
0.0381
b0.0001
0.0127
0.0184
0.7386
0.0345
0.7571
0.2142
–0.0568
0.0058
−0.0153
0.0059
−0.0447
0.0499
0.0007
0.0001
0.0530
0.4054
0.7574
0.0138
0.5544
0.0629
−0.0025
0.0706
0.0214
0.0680
0.0373
b0.0001
0.0022
0.5931
0.0068
0.4209
0.0138
0.3143
0.0419
−0.0044
0.0618
0.0938
0.0840
0.0496
0.0001
0.0216
0.2281
0.0112
0.0001
0.0003
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borns (and least common in autumn borns), while the
Hyperthymic is most common in spring and autumn borns
(and least common in summer and winter borns). This means
that these two basic temperaments show opposite patterns
with respect to birth seasonality, which is in line with clinical
observations (Rihmer et al., 2010). Cyclothymic and Irritable
temperaments on the other hand show a similar pattern of
association with birth season. This is also in line with the
classical concept of these two latter affective temperaments;
that is, both incorporate the Depressive and the Hyperthymic
components. However, in case of the Cyclothymic tempera-
ment, depression and hyperthymia occur in an alternative
periodic pattern, while in the case of the Irritable tempera-
ment they are present simultaneously.
It is interesting that the Hyperthymic temperament and
the remaining four temperaments – containing more or less
of a depressive component – differ from each other in several
clinical and biological aspects. In contrast to the Hyperthymic
temperament, the Depressive, Cyclothymic, Irritable and
Anxious temperaments show a significant association with
the ‘s’ allele of the serotonin transporter gene (Gonda et al.,
2006, 2009), with suicidal behavior (Vazquez et al., 2010;
Pompili et al., 2008b; Rihmer et al., 2009) and with deep
white matter abnormalities (Serafini et al., 2011) indicating
that Hyperthymic temperament seems to be a separate
dimension compared to the other affective temperaments.
The finding that the Anxious temperament did not show an
association with birth season is also well in line with clinical
observations indicating that, unlike affective disorders and
suicide, the course of anxiety disorders shows no seasonal
pattern, and with results from prior studies showing that –
except for panic disorder – anxiety disorders show no season
of birth effect (Castrogiovanni et al., 1998, 1999). It is also
well known that panic disorder is often manifested in
comorbidity with bipolar disorders suggesting a possible
common point in etiology (Logue et al., 2009; Goodwin and
Hoven, 2002; Szadoczky et al., 1998) which may in part
explain the effect of birth season in the case of panic disorder.
Another very important finding is that the association of
Hyperthymic temperament with birth season (spring–au-
tumn peak and summer–winter low) coincides with the birth
season pattern of bipolar I patients (Rihmer, 1980) who are
predominantly characterized by Hyperthymic temperament
(Rihmer et al., 2010), and also with the seasonality of hospital
admissions due to mania (Rihmer, 1980). Birth seasonality
associated with Depressive temperament (summer–winter
peak and spring–autumn low), on the other hand, coincides
with the birth seasons associated with bipolar II depression
(Rihmer, 1980) which is characterized by Depressive and
Cyclothymic temperament (Rihmer et al., 2010), and hospital
admissions of bipolar II patients due to depression follow the
same pattern (Rihmer, 1980). It is an interesting finding that
the Anxious temperament did not show an association with
season of birth. It is, however, well in line with clinical
observations, that anxiety disorders, unlike affective disor-
ders and suicide, show no seasonal fluctuation, and this way
our result may shed further light on the etiopathology of
affective disorders as well.
Our results are novel, since no study so far has investi-
gated the effect of birth season on affective temperaments.
However, in earlier studies a significant association between
season of birth and other personality traits has been reported.
It has consistently been found in several studies that Novelty
Seeking (NS) scores are significantly lower in subjects born
during winter compared to those born during summer in
adult women, although in adolescent women the pattern is
the opposite with higher NS scores for those born during
winter (Chotai et al., 2001, 2003a, 2009), suggesting that
women born during winter exhibit a sharper rise during their
adolescence and then a steeper decrease during adulthood in
novelty seeking compared to women born during summer,
which suggest an association between season of birth and
personality development throughout the life span (Chotai
et al., 2009). Reward Dependence was also found to be
strongly associated with season of birth (Chotai et al., 2009);
however, the results are somewhat mixed. In a Finnish study
men born during spring had significantly lower RD scores
compared to men born in autumn (Chotai et al., 2009), while
in a Swedish study significant results were found only in case
of pooled genders, and RD peak was found in those born in
December(Chotai et al., 2001), which the authors explain as a
result of reward dependence being modulated by an
interaction between dopamine and other neurotransmitters
(Kim et al., 2006). Similarly, classical Big Five and Eysenckian
personality dimensions have also been reported to be
associated with birth season. In a study using Neo-Pi-R,
Agreeableness scores weresignificantly lowerin winterborns
compared to other subjects, with a marginally significant
higher score in individuals born in March and April (Tochigi
et al., 2004). In another study using the Big Five Observer,
however, only scores on the Conscientiousness scale tended
to show a significant association with birth season, with
lower scores for summer born individuals compared to other
subjects, but the association was significant in males (Tonetti
et al., 2009). In case of Extraversion and Neuroticism, those
bornduring thecoldmonthswere reportedto scorehigheron
Extraversion and lower on Neuroticism (Forlano and Ehrlich,
1941), and in another study summer borns scored higher on
Neuroticism (Gupta, 1992). In a third study winter born
young adults were reported to score significantly higher on
Neuroticism compared to autumn borns, who also scored
higher than summer borns, while in case of Extraversion,
autumn borns scored significantly higher compared to
summer borns (Chichilenko and Babarash, 2001) indicating
Hyperthymic
Cyclothymic
Irritable
Depressive
Anxious
SpringSummer Autumn Winter
0,10
0,15
0,20
0,25
0,30
0,35
0,40
0,45
0,50
0,55
0,60
0,65
Fig. 1. Mean scores of each affective temperament by birth season.
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that the results are somewhat contradicting for Neuroticism.
These studies therefore support a strong association between
season of birth and personality and our results yield further
evidence for this association using a new approach to
personality and temperament. Earlier moderately strong
correlations have been described between affective tempera-
ments and TCI and NEO-Pi-R dimensions (Rozsa et al., 2008).
Considering those personality traits which have previously
been shown to be associated with season of birth, Neuroti-
cism had a moderately strong positive correlation with
Depressive, Cyclothymic, Irritable and Anxious and a moder-
ately strong negative correlation with the Hyperthymic
temperament. Hyperthymic temperament also showed a
moderately strong positive correlation with Extraversion. A
strong negative correlation with Conscientiousness was
observable in case of the Cyclothymic temperament (Rozsa
et al., 2008). Interestingly, the birth season associations of
affective temperaments partially fit our expectations based
on these correlations in case of the Hyperthymic tempera-
ment, where scores are higher in those born during spring
and autumn (partially corresponding to higher scores during
cold months and autumn as expected due to a positive
correlation with Extraversion), while Cyclothymic scores are
higher in summer borns as expected, since the Cyclothymic
temperament shows a strong negative correlation with
Conscientiousness, where scores are lower in summer
borns. This gives further support to the association between
affective temperaments and birth season.
Seasonal factors may play a role during gestation or the
perinatal period on monomamine gene expression (Chotai
et al., 2003b, 2009). Accordingly, an association between
monoamine metabolite levels in the cerebrospinal fluid and
season of birth has been reported in several studies. Levels of
the dopamine metabolite homovanillic acid (HVA), and the
noradrenaline metabolite 3-Methoxy-4-hydroxyphenylgly-
col (MHPG) were found to be significantly lower in those
born in summer compared to those born in winter, while
the level of serotonin metabolite 5-hydroxyindoleacetic acid
(5-HIAA) was lower in those born in spring compared to
those born in autumn, and in some studies in those born
during winter (Chotai and Asberg, 1999; Chotai and Adolfsson,
2002; Chotai et al., 2006). The observed fluctuation in central
monoamine levels paralleled the results concerning the
association of birth seasons and personality dimensions.
Novelty seeking is thought to be modulated by dopaminergic
function, with high novelty seeking associated with low
dopaminergic activity (Cloninger et al., 1993), and winter
borns exhibit both significantly lower novelty seeking and
higher MHPG levels. On the other hand, results concerning the
association between birth seasonality and suicidal behavior
described in several studies (Salib and Cortina-Borja, 2006;
Dome et al., 2010) are in line with the seasonal fluctuation in
serotonin turnover (Praschak-Rieder et al., 2008). The neuro-
biochemistry of affective temperaments have not been studied
in detail so far; however, these results indicate that differential
monoamine function corresponding to birth season may play
an important role in the development of affective tempera-
ments as well.
Our results therefore add to the mounting evidence that –
beside the relationship between season of birth and unipolar
and bipolar major mood disorders (Torrey et al., 1997; Mino
et al., 2000; Rihmer, 1980) – there is a strong association
between season of birth and personality, extending the
results to affective temperaments as well. This is especially
interesting, since affective temperaments are conceived as
the subaffective and subclinical manifestations of major and
minor affective disorders indicating a risk for the develop-
ment of this disease and also exerting a possible patoplastic
effect (Rihmer et al., 2010; Akiskal and Akiskal, 2005, 2007),
thus our results also have a clinical significance. Furthermore,
as the literature on the relationship between season of birth
and season of incidence of different mood episodes in the
same sample of mood disorder patients is almost lacking
(Rihmer, 1980), further studies are needed to explore the
possible connection between these phenomena in patient
populations as well.
Our study has a number of limitations. Firstly, the sample
size limits the generalization of the present findings, and
although the total number of participants was 366, the
number of subjects in each seasonal subgroups was much
smaller, ranging from 88 to 100. Furthermore, the instrument
to assess temperament, althoughreliable andcommonlyused
in varioussetting,wasnotmatchedwithat leastanotherscale
to verify validity. Third, there may have been factors
decreasing the validity of the scales, such as social desirability
(Banister et al., 1994). It would be of interest to explore the
results of this study in other clinical and nonclinical samples.
Another potential limitation is the subtype of no clinical
sample, students of “Investment” is a very specific population,
in which affective temperament traits could influence their
academic interests and/or elections (Figueira et al., 2010;
Akiskal and Akiskal, 2007). We also did not report psycho-
social variables of subjects and assessment of psychopathol-
ogy was not performed.
Role of the funding sources
There were no funding sources involved in the work described in this
paper.
Conflict of interest
The authors have no conflict of interest to declare.
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