Quantitative motor activity differentiates schizophrenia subtypes.

Abstract

Motor symptoms are frequent in schizophrenia and relevant to the diagnosis of subtypes. However, the assessment has been limited to observations recorded in scales and experimental designs. The aim of this study was to use wrist actigraphy to obtain motor activity data in 3 schizophrenia subtypes.
In total, 60 patients with schizophrenia (35 paranoid, 12 catatonic, 13 disorganized) were investigated using continuous wrist actigraphy over 24 h in an inpatient setting on average 38 days after admission. Data of the wakeful hours of the day were analyzed.
The activity level was predicted by schizophrenia subtype and by the type of antipsychotic medication. The movement index and mean duration of uninterrupted immobility were found to be predicted only by the schizophrenia subtype. Age, gender, duration of illness and chlorpromazine equivalents did not contribute to the variance of the activity data. A MANOVA demonstrated the significant differences in the 3 parameters between schizophrenia subtypes (p = 0.001). Patients with catatonic schizophrenia had lower activity levels, a lower movement index and a longer duration of immobility than those with paranoid schizophrenia.
Schizophrenia subtypes can be differentiated using objective measures of quantitative motor activity. The increased duration of immobility appears to be the special feature of catatonic schizophrenia.

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Original Paper
Neuropsychobiology 2009;60:80–86
DOI: 10.1159/000236448
Quantitative Motor Activity
Differentiates Schizophrenia Subtypes
Sebastian Walther Helge Horn Nadja Razavi Philipp Koschorke
Thomas J. Müller Werner Strik
University Hospital of Psychiatry, University of Bern, Bern , Switzerland

quantitative motor activity. The increased duration of im-
mobility appears to be the special feature of catatonic
schizophrenia.
Copyright © 2009 S. Karger AG, Basel
Introduction
The quality and frequency of motor symptoms in
schizophrenia have been accorded importance in the di-
agnosis of subtypes and were described in detail in clas-
sical psychopathology [1, 2] . Today, their prevalence and
thus the diagnosis of catatonia appears to be decreasing,
and their clinical distinction from neuroleptic side effects
is unreliable [3, 4] .
Motor symptoms, however, occur frequently in schizo-
phrenia. In fact, 50% of a schizophrenia group were found
to present at least 1 motor symptom during the acute
stage [5] . Further, motor symptoms are still part of the
diagnostic criteria for schizophrenia in DSM-IV and
ICD-10. They are necessary for the diagnosis of the cata-
tonic subtype of schizophrenia even if the mere presence
of motor symptoms is not sufficient in either classifica-
tion system. Instead, a predominance of motor symptoms
is required to allow the diagnosis of catatonia.
Research interest in motor symptoms of schizophrenia
has increased within the past 2 decades, and several stud-
ies suggest an important role for the motor system in this
disorder. The development of motor abilities has been re-
Key Words
Actigraphy ? Catatonia ? Psychosis ? Motor retardation ?
Negative syndrome ? Antipsychotics
Abstract
Background: Motor symptoms are frequent in schizophre-
nia and relevant to the diagnosis of subtypes. However, the
assessment has been limited to observations recorded in
scales and experimental designs. The aim of this study was
to use wrist actigraphy to obtain motor activity data in 3
schizophrenia subtypes. Methods: In total, 60 patients
with schizophrenia (35 paranoid, 12 catatonic, 13 disorga-
nized) were investigated using continuous wrist actigraphy
over 24 h in an inpatient setting on average 38 days after
admission. Data of the wakeful hours of the day were ana-
lyzed. Results: The activity level was predicted by schizo-
phrenia subtype and by the type of antipsychotic medica-
tion. The movement index and mean duration of
uninterrupted immobility were found to be predicted only
by the schizophrenia subtype. Age, gender, duration of ill-
ness and chlorpromazine equivalents did not contribute to
the variance of the activity data. A MANOVA demonstrated
the significant differences in the 3 parameters between
schizophrenia subtypes (p = 0.001). Patients with catatonic
schizophrenia had lower activity levels, a lower movement
index and a longer duration of immobility than those with
paranoid schizophrenia. Conclusions: Schizophrenia sub-
types can be differentiated using objective measures of
Received: January 27, 2009
Accepted after revision: June 23, 2009
Published online: September 10, 2009
Sebastian Walther, MD
University Hospital of Psychiatry
Bolligenstrasse 111
CH–3060 Bern (Switzerland)
Tel. +41 31 930 9111, Fax +41 31 930 9404, E-Mail walther@puk.unibe.ch
© 2009 S. Karger AG, Basel
0302–282X/09/0602–0080$26.00/0
Accessible online at:
www.karger.com/nps

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Motor Activity in Schizophrenia
Subtypes
Neuropsychobiology 2009;60:80–86
81
peatedly shown to be delayed in children who later suffer
from schizophrenia [6–8] . A body of evidence supports
impaired motor control and motor sequencing in schizo-
phrenia [9–11] . Reduced volume in the cerebellum in
schizophrenia was reported [8, 12] and thought to relate to
disturbances of the motor system. Gait disturbances have
been observed in patients with schizophrenia [13] as well
as bradykinesia in 8–18% of the neuroleptic-naïve patients
[14] . Parkinsonism and dyskinesia were demonstrated to
be related to psychopathology in neuroleptic-naïve first-
episode patients [15] . In addition, several studies on neu-
rological soft signs have reported motor disturbances in
both treated and untreated schizophrenia [16–19] .
The assessment of motor symptoms, however, is chal-
lenging and often limited to clinical observation and spe-
cific rating scales. On the other hand, studies relying on
quantitative measurements usually depended on labora-
tory settings [11, 20, 21] . To obtain information about the
motor behavior of schizophrenic patients in naturalistic
environments, objective quantitative measurements are
needed.
Actigraphy is a validated tool in sleep medicine and has
become important for motion analysis in psychiatric re-
search [22] . However, only few studies on quantitative mo-
tor activity during wakefulness have been conducted in
schizophrenia using actigraphy [23–25] . Farrow et al. [23,
24] reported a negative correlation of the cumulated activ-
ity counts with avolition. We have reported higher motor
activity levels (AL) in cycloid psychoses as compared to
paranoid schizophrenia [26] and poor correlation between
objective motor activity and expert ratings [27] . In addi-
tion, disturbances of the sleep-wake cycle as measured by
actigraphy were reported in schizophrenia [28–30] .
We were interested whether DSM-IV schizophrenia
subtypes would differ with regard to quantitative motor
activity as measured by actigraphy. In particular, we hy-
pothesized that specific motor features of catatonic
schizophrenia could be identified compared to the other
schizophrenic subtypes. Further, based on the fact that
the clinical distinction between catatonic and drug-
induced movement disorders is unreliable, we explored
the possibility whether objective movement parameters
would be more reliable to discriminate them.
Subjects and Methods
Subjects
Study participants were recruited during the first 3 weeks after
admission to the inpatient department of the University Hospital
of Psychiatry Bern, Switzerland. The inclusion criterion was a
DSM-IV diagnosis of schizophrenia based upon clinical inter-
views and review of all records available, taking into account the
longitudinal course of the disorder. The exclusion criteria were a
history of or concomitant neurological or medical disorder, or
substance abuse (except for nicotine). Participation was unpaid.
Sixty-three patients were included in the study with an overlap
with the sample reported earlier [27] . Three of the patients re-
ceived anticholinergic drugs which may influence motor activity
and were excluded from the final analyses.
Chlorpromazine equivalents were calculated according to Rey
et al. [31] and Woods [32] . In addition, 14 patients were also treated
with antidepressants for the negative syndrome in schizophrenia.
Seven received a selective serotonin reuptake inhibitor, 1 a selective
noradrenaline reuptake inhibitor , 3 a selective serotonin and nor-
adrenaline reuptake inhibitor, and 3 patients were on tricyclic anti-
depressants. No difference in antidepressant prescription was de-
tected between the schizophrenia subgroups ( ? 2 = 5.515; d.f. = 8; p
= 0.773). The demographic and clinical variables are displayed in
table 1 . After a complete explanation of the aims and procedures of
the study, the patients provided written informed consent. The pro-
cedures are in accordance with the declaration of Helsinki and had
been approved by the local ethics committee (KEK No. 208/06).
Measures
The patients were interviewed and assessed using the Positive
and Negative Syndrome Scale (PANSS) [33] . In addition, they
wore an actigraph (Actiwatch ? , Cambridge Neurotechnology
Inc., UK) on the wrist of the nondominant arm for 24 consecutive
hours for the continuous recording of motor activity. Handedness
was determined by asking the patients about the preferred hand
when writing, brushing teeth and eating with a spoon.
Motor Activity Parameters
Movement counts of the actigraph were stored in 2-second in-
tervals, allowing continuous recording for a maximum of 36 h on
the 64-kB memory. We chose the smallest possible interval to
achieve maximum temporal resolution. The nondominant arm
was chosen because it reflects average movement during day- and
nighttime, while actigraphy in the dominant arm represents max-
imum movements that are strongly related to manual work or
activities [34] . The start of measurement varied between 10:
and 15:
cycle, so each hour of the day was covered. In 3 participants (1 of
each subtype), however, we failed to record complete 24-hour da-
tasets as these patients removed their actigraphs during sleep.
Motor activity is subject to circadian rhythms. By investigating
inpatients of 1 large psychiatric university hospital we had the
chance to normalize external and social rhythms. The patients on
all wards get up around 7:
11:
eral group activities during the day and have social contact until
22:
performed exclusively during weekdays to assure that there was
equal impact of group therapies across the participants. At the end
of the recording, the patients were asked to provide sleep log in-
formation and to fill in the Pittsburgh Sleep Quality Index [35] .
00
00, but for the analyses we included the whole 24-hour
00, have breakfast at 07:
30, lunch at
30 and dinner at around 18:
00. Also, they are engaged in sev-
00, when the lights are usually turned off. Measurements were
Data Analysis
The data were analyzed using Sleep Analysis 5 ? (Cambridge
Neurotechnology) and EXCEL ? templates for further analyses.

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Neuropsychobiology 2009;60:80–86
82
Using the sleep log information, we removed data collected dur-
ing sleep. We chose to extract 3 parameters from the data that had
previously been described [34] and used in schizophrenia [26, 27] .
AL is the mean number of activity counts per hour. The move-
ment index (MI) is the percentage of periods with an activity
count 1 0, reflecting the proportion of 2-second periods with ac-
tivity or immobility. The mean duration of uninterrupted immo-
bility periods (MIP) provides a global measure of the distribution
and number of immobility periods. Further analyses were per-
formed using SPSS ? 15.0.
General linear models (GLM) were computed for AL, MI and
MIP as dependent variables using Wald ? 2 . The main effects of the
following predictors were compared: schizophrenia subtype, age,
gender, type of antipsychotic medication, chlorpromazine equiva-
lents, number of episodes and duration of illness. Afterwards, a
MANOVA using Wilks’ ? with AL, MI and MIP as dependent
variables and schizophrenia subtype as between-subject variable
was performed. Bonferroni correction was applied for multiple
comparisons. Differences between groups in the descriptive sta-
tistics were tested using 1-way ANOVAs or ? 2 tests when appropri-
ate. Correlations of activity parameters were performed using
Pearson’s correlation. All levels of significance are 2-tailed.
Results
Motor Activity during Wakefulness
For each of the motor activity parameters a GLM was
computed with the predictors schizophrenia subtype,
chlorpromazine equivalents, type of antipsychotic drugs
used (none, atypical, typical or both), age, gender, num-
ber of episodes and duration of illness. The GLM of AL
demonstrated a significant main effect for schizophrenia
subtype ( ? 2 = 6.055, p = 0.014) and type of antipsychotic
treatment ( ? 2 = 3.861, p = 0.049). However, an ANOVA
for AL with schizophrenia subtype and type of antipsy-
chotic failed to detect an interaction of both factors
(F 5, 60 = 0.984, p = 0.437).
When we performed an independent t test on AL, we
found a nonsignificant trend towards higher AL in the
patients treated with atypical antipsychotic drugs only
(T 40 = –1.853, d.f. = 38, p = 0.072). However, the type of
antipsychotic drug used was comparable between the
schizophrenia subtypes (see table 1 ).
The GLM of MI found a significant main effect only
for schizophrenia subtype ( ? 2 = 5.968, p = 0.015). Simi-
larly, the GLM of MIP showed a significant main effect
only for the predictor schizophrenia subtype ( ? 2 = 11.563,
p ! 0.001). None of the other predictors had a significant
main effect on any of the activity parameters.
As the GLMs revealed schizophrenia subtype to have
a main effect on motor activity parameters, these 3 pa-
rameters were entered as dependent variables into a
MANOVA with schizophrenia subtype as between-sub-
ject factor. Schizophrenia subtype demonstrated a signif-
icant overall effect (Wilks’ ? : F 6, 60 = 4.320, p = 0.001).
Significant differences between schizophrenia subtypes
Table 1. Characteristics of the schizophrenia subtypes
CharacteristicSchizophrenia subtype
paranoid (n = 35)
n%
Comparison
?2
catatonic (n = 12)
n
disorganized (n = 13)
n
d.f.p
%%
Male gender
Antipsychotic treatment
None
Typical
Atypical
Both
1851.4650.0969.21.36520.523
2
2
5.3
5.7
68.6
20.0
0
2
5
5
01
2
5
5
7.7
15.4
38.5
38.5
7.15160.236
16.7
41.7
41.7
24
7
MeanSD MeanSDMeanSDFd.f.p
Age, years
Duration of illness, years
Episodes
Chlorpromazine equivalents
PANSS positive score
PANSS negative score
PANSS total score
39.60
10.97
7.31
488.45
17.60
17.06
75.51
9.64
8.84
6.21
45.50
6.34
4.25
566.13
14.92
20.00
79.92
12.19
5.70
2.96
537.62
4.03
7.66
17.60
36.23
14.85
9.38
718.46
15.85
20.77
84.46
10.26
10.50
3.55
659.00
5.44
5.54
18.68
2.602
2.967
3.049
1.143
1.377
2.353
1.439
2
2
2
2
2
2
2
0.083
0.059
0.055
0.326
0.261
0.104
0.246
350.35
5.53
5.43
15.51

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Motor Activity in Schizophrenia
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were detected in each of the dependent variables: AL
(F 2, 60 = 4.629, p = 0.014), MI (F 2, 60 = 3.615, p = 0.033) and
MIP (F 2, 60 = 10.397, p ! 0.001). The post hoc t-tests re-
vealed differences between patients with catatonic and
paranoid schizophrenia (see fig. 1 a–c). Indeed, in para-
noid schizophrenia the highest AL and MI were found,
while patients with catatonic schizophrenia displayed the
longest duration of immobility.
AL correlated negatively with the PANSS negative
subscore. On the other hand, the PANSS positive sub-
score correlated positively with MI and negatively with
MIP (see table 2 ). Therefore, stronger negative syndrome
severity was associated with less activity, while stronger
positive syndrome scores indicated shorter immobility
and a higher proportion of active periods.
The PANSS item score for motor retardation was high-
est among catatonia patients ( ? 2 = 19.337, d.f. = 10, p =
0.008). However, motor retardation to some extent was
rated frequently in each subtype (paranoid 37%, cataton-
ic 91%, disorganized 47%). As expected, specific symp-
toms such as mannerism were most frequent among pa-
tients with catatonic schizophrenia (92%; ? 2 = 28.880,
d.f. = 12, p ! 0.001), while other items of the negative syn-
drome were equally rated between the groups (social
avoidance: p = 0.237; lack of spontaneity: p = 0.427; blunt-
ed affect: p = 0.499). Likewise, the PANSS items distur-
bance of volition and depression were not rated differ-
ently between the groups (p = 0.147 and p = 0.518).
Sleep
The actual sleep time differed between the groups (see
table 3 ). No variations were identified in terms of sleep
quality and motor activity during sleep.
Discussion
The results demonstrate differences in motor activity
during wakefulness in schizophrenia subtypes and sup-
port our hypothesis. In fact, they diverge in terms of the
magnitude of activity (AL), the relative amount of active
periods (MI) and the mean duration of immobility (MIP).
Patients with catatonic schizophrenia had a lower overall
AL, lower MI and longer immobility periods as com-
pared to patients with paranoid schizophrenia. No post
hoc differences were found between the disorganized and
other subtypes. Even though the type of antipsychotic
medication had some unspecific effect on AL, there was
no interaction of antipsychotic and subtype associated
with AL. All other factors presumably influencing motor
activity, such as age, gender, chlorpromazine equivalents
and duration of illness, had no effect on the parameters
tested.
Table 2. Correlation of motor activity parameters and PANSS
PANSS
positive score
r
PANSS
negative score
r
PANSS
total score
rppp
AL, counts/h
MI, %
MIP, s
0.181 0.167
0.286 0.027*
–0.286 0.027*
–0.351 0.006*
–0.204 0.118
–0.025 0.848
–0.225 0.084
–0.087 0.507
–0.111 0.398
* p < 0.05.
0
Activity level (counts/h)
Paranoid
5,000
10,000
15,000
20,000
n = 35
Catatonic
n = 12
p = 0.016
Disorganized
n = 13
0
Movement index (%)
Paranoid
10
20
30
40
n = 35
Catatonic
n = 12
p = 0.045
Disorganized
n = 13
50
Schizophrenia typeSchizophrenia type
0
Mean duration of
uninterrupted immobility (s)
Paranoid
2
4
6
n = 35
Catatonic
n = 12
p < 0.001
Disorganized
n = 13
Schizophrenia type
a
bc
Fig. 1. Quantitative motor activity in schizophrenia subtypes. Bars display means + 1 SD. Post hoc comparisons
using Bonferroni correction.

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Neuropsychobiology 2009;60:80–86
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As in an earlier study [27] , reduced magnitude of motor
activity (AL) was associated with higher PANSS negative
syndrome scores. In contrast, with higher PANSS positive
syndrome scores we found a shorter duration of immobil-
ity (MIP) and a higher proportion of active periods (MI).
Both correlations indicated less rest during marked posi-
tive syndromes. Some single PANSS items might be more
relevant to motor activity than others. As expected, motor
retardation and mannerisms were rated most frequently
in catatonic schizophrenia. Depression, lack of spontane-
ity, disturbance of volition and social avoidance displayed
no differences between the subtypes.
In the GLMs we found no impact of chlorpromazine
equivalents on the motor activity parameters, nor could we
observe an impact of the type of antipsychotic adminis-
tered on MIP and MI. In AL, however, there was a differ-
ence between the types of antipsychotic administered. On
the other hand, we failed to find specific differences in the
post hoc tests. In addition, there was no interaction of the
factors antipsychotic medication and subtype of schizo-
phrenia. A nonsignificant trend towards higher activity
was observed in AL when we compared atypical versus typ-
ical antipsychotics. This ambiguous result is in line with
the finding that atypical antipsychotic drugs vary substan-
tially in their ability to induce extrapyramidal side effects
[36] . However, there were no differences between the groups
in terms of the prescription of antipsychotic drugs.
The most prominent difference between the subtypes
was found in the duration of immobility. Thus, our re-
sults suggest that the duration of immobility could reflect
specific catatonic symptomatology, the intrinsic motor
disturbances in schizophrenia [15] or both.
Catatonic patients exhibit an irregular pattern of activ-
ity with longer periods of immobility followed by active
phases. This could also explain the low average AL because
longer immobility would contribute to lower AL. Similar-
ly, longer duration of immobility would decrease the pro-
portion of active periods in favor of inactive periods and
thereby lead to a lower MI. Our results suggest that motor
activity in catatonic schizophrenia is characterized by in-
termittent inhibitions preventing the patients from regu-
lar, fluent movement patterns. These phenomena, interest-
ingly, are usually not perceived by clinical observation and
lack operationalization in standard psychopathological
scales and diagnostic systems. In fact, no significant dif-
ference in the negative syndrome was detected between the
subgroups. Motor retardation as a PANSS item was fre-
quent in all subgroups, even though the scores in catatonia
were higher. Therefore, the categorization of single pa-
tients as catatonic simply by the observation of reduced
motor activity is imprecise. Employing actigraphic mea-
sures such as the duration of immobility could increase the
quality of diagnosis, adding an objective parameter to the
clinical observation of rather complex catatonic move-
ment patterns like mannerisms, stereotypy, echophenom-
ena, perseveration and automatic obedience.
Patients with catatonic schizophrenia were shown to
have specific deficits in decision making and set shifting,
neuropsychological measures associated with ventral
prefrontal cortical function [37] . Indeed, the medial pre-
frontal cortex is critical to the evaluation of the relevance
of cognitive goals and motor acts [38] . Findings from
neuroimaging studies in catatonic schizophrenia report-
ed a reduced cerebral blood flow in the parietal lobe [39,
Table 3. Sleep data
Schizophrenia type
paranoid
mean
F d.f.p
catatonic
mean
disorganized
meanSDSD SD
PSQI
Sleep efficiency, %
Sleep latency, hh:mm:ss
Actual sleep time, hh:mm:ss
Immobile time percent, %
Sleep AL, counts/h
Sleep MI, %
Sleep MIP, s
6.50
84.40
00:28:32
07:41:38
91.95
1,814.91
4.65
78.55
3.57
6.71
00:31:06
01:36:42
5.08
1,449.91
3.26
60.05
8.00
86.22
00:27:11
08:55:05
91.95
1,440.07
4.52
79.33
2.66
7.66
00:17:41
01:28:16
7.28
1,023.58
3.31
54.24
5.83
79.56
00:41:30
06:09:45
88.21
1,763.93
5.46
53.23
3.10
8.37
00:45:16
03:21:06
8.25
1,671.15
4.34
33.75
1.393
2.724
0.775
5.008
1.603
0.284
0.285
1.034
2
2
2
2
2
2
2
2
0.257
0.075
0.466
0.010*
0.211
0.754
0.753
0.363
* p = 0.008 (catatonic > disorganized; post hoc t test, Bonferroni correction).