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[28]
[32]
of Mental Disorders, fifth edition (DSM-V). The for the schizophrenic and depressive patients, the
inclusion criterion for all participants was that participants were asked to complete a sleep log for two
they be between 18 and 65 years of age, and the weeks. It consisted of the following six sleep variables: (1)
exclusion criteria for the patients with schizophrenia “total sleep time”；(2) “how many minutes awake during
or depression were substance abuse, epilepsy, and the night”；(3) “how many minutes awake before falling
other neurological disorders. Finally, all patients asleep”; (4) “how relaxing was your sleep”; (5) “did you
took part voluntarily without any inducement and feel exhausted”; (6) “how was your average performance
signed the informed consent form. level today”. The sleep log was to be completed every
morning just after awakening and every evening just
Material before falling asleep. [33] Completing the sleep log took
BDI-II approximately 10 min a day, 140 min in total.
The Beck Depression Inventory-II (BDI-II) [29] was
used to assess depression severity. The BDI-II is Procedure
a 21-item self-report inventory, and each item is Every participant in the group of patients with
rated on a 4-point scale (i.e. from 0 to 3). Thus, an depression was asked to complete the BDI-II
individual’s scoring range would lie between 0 and and the PSQI. The PANSS was completed by the
63. The higher the total scores on the BDI-II, the more patient’s psychiatrist in the group of patients with
severe the depressive symptoms of the patients are. schizophrenia, and these patients were also asked
to complete the PSQI. All participants were asked
PANSS to keep a sleep log and return it to their clinical
In addition, the Positive and Negative Syndrome Scale psychologist at the end of the two weeks. At the end of
(PANSS) [30] was used to measure the symptom severity the study, a debriefing was offered to all participants,
of the patients with schizophrenia. The PANSS has in which they were individually informed of their
to be filled in by a psychiatrist. It consists of three test results. The study was approved by the local
subscales: the positive scale, the negative scale and ethics committee (Ärztekammer Nordrhein, number:
the general psychopathology scale. The scoring range 2008331); moreover, the clinical trial has officially
for an individual is between 7 and 49 for the positive been registered under number NTR3132 at the Dutch
scale, 7 and 49 for the negative scale, and 16 and 112 Trial Register (see also http://www.trialregister.nl/
for the general psychopathology scale; as a result, the
total scores on the PANSS are between 30 and 210. trialreg/admin/rctview.asp? TC = 3132). Finally,
The higher the total scores on the PANSS are, the the study was performed in accordance with the
more severe the positive and negative symptoms of Declaration of Helsinki (http://www.wma.net/
the individuals with schizophrenia are. en/30publications/10policies/b3/).

Design and statistics
PSQI
The Pittsburgh Sleep Quality Index (PSQI) was An experimental design was used in which the first
[31]
used to measure the subjective quality of sleep of the categorical dependent variable was called “Absolute
patients with schizophrenia or depression. The PSQI Treatment Adherence”; it was measured by using
is a self-report inventory and measures sleep quality the returned sleep logs (i.e. if the patient returned
and patterns of sleep. It has seven separate domains: (1) the sleep log, the patient was considered as being
“subjective sleep quality”; (2) “sleep latency”; (3) “sleep treatment adherent vs. if the patient did not return
duration”; (4) “habitual sleep efficiency”; (5) “sleep the sleep log, the patient was considered as not
disturbances”; (6) “use of sleep medication”; and (7) being treatment adherent). The second continuous
“daytime dysfunction over the last month”. Individuals dependent variable was called “Degree of Treatment
score all items on a Likert scale, ranging from 0 to 3. As Adherence” because it consisted of the total number
a result, the total scores on the PSQI are between 0 and of days the participants had completed the sleep log,
21, and the higher the total PSQI score is, the poorer with 0 day meaning a very low degree of treatment
the quality of sleep is. In daily clinical practice, often adherence and 14 days meaning a very high degree
a cut-off score of 5 [31] is used, meaning that participants of treatment adherence. In other words, “Absolute
who score below 5 have a good quality of sleep and Treatment Adherence” showed whether a patient
participants who score above 5 have a poor quality of returned the sleep log or not while “Degree of
sleep. In the present study, the total PSQI scores were Treatment Adherence” showed to what degree the
used for further analyses. patient was treatment adherent. Note that in the
present study, a very narrow definition of the word
Sleep log “treatment” was used (e.g. completing and returning
As part of the treatment adherence measurements a sleep log) and did not include any pharmacological

Neuroimmunol Neuroinflammation | Volume 3 | May 20, 2016 111