General description of the study
The cross-sectional study reported here is part of the 2009–2010 Psychiatric Morbidity Survey carried out in Greece using a nationally representative sample of the adult population (18 – 70 years). The study was organized by the Ministry of Health and carried out by the University of Ioannina. Data collection was conducted between September 2009 and February 2010. Regarding provision of healthcare in Greece, there are 7 “Regional Health Authorities” (RHA) covering all geographic regions of the country. Eligible for participation were all adults living in households in each of the seven RHAs. Due to the high costs incurred by sampling all islands of the Aegean, Crete was excluded from the sampling (as Crete has been covered in the past by other smaller scale surveys), therefore the sample included participants from all areas of Greece excluding Crete.
Sampling methodology was designed and implemented by a research agency in Greece with substantial experience in conducting nationwide surveys of social or political issues using representative samples of the general adult population of Greece. According to the latest Population Census (2001) the survey population consisted of approximately 7,200,000 individuals. A three-stage sampling design was used with enumerator areas (one or more unified city blocks) based on the 2001 census survey selected at the first stage, households within the selected areas at the second stage and individuals within the households at the third stage.
The primary sampling units (enumerator areas) were first stratified by allocating the Municipalities and Communes included in each Region according to the degree of urbanization (stratum 1: urban areas; stratum 2: semi-urban; stratum 3: rural areas). The stratification for the two major cities, Athens and Thessaloniki, were different (Athens was divided into 31 strata of equal size and Thessaloniki into 9 strata). The projected sample size for the whole survey was 9,800 individuals with a sampling fraction 1/λ for each stratum considered constant and equal to 0.085%.
At the first stage of the sampling procedure primary sampling units (enumerator areas) had a probability of being selected proportional to their size (number of households according to the 2001 census). At the second stage from each selected area (primary sampling unit) the sample of secondary units (households) was selected. Actually, in the second stage a random systematic sample of households was drawn. Systematic sampling is functionally similar to random sampling because each element (household) had a known and equal probability to be selected. Systematic sampling starts by selecting a random starting point (using maps of the enumerator areas) and then every kth element in the sampling frame is selected, where k is the sampling interval. In any selected primary unit, the sample size was determined from the sampling interval which was calculated using data from the 1st stage. At the third stage one eligible member (aged 18–70 years) of the household was selected using simple random sampling.
Data collection and response rate
In each RHA a pool of 20 trained researchers and 2 supervisors were employed. All instruments used were computerized and responses to the questions/interview were entered directly to a laptop computer. The average time for completion of the instrument was from 30 to 45 minutes depending on the psychopathology. Approximately 35% of the participants entered their data into the laptop without any further assistance from the interviewer after the first guidance. The remaining 65% required some help from the interviewer.
Overall response rate was 54% with a range between 51% and 60% between regions. Refusals were more common from women and the middle aged participants (40–55). Differences between the sample and the 2001 census population data were small. A full detail of the study design, sampling procedures, sampling distribution within each regional health authority and data collection are available from the technical reports submitted to the Ministry of Health and are available by the authors on request.
Measurement of psychiatric morbidity
Psychiatric morbidity was assessed with the revised clinical interview schedule (CIS-R), a fully structured psychiatric interview designed to be used by trained lay interviewers
]. The CIS-R was the main instrument used in the national psychiatric morbidity surveys in the UK
] and has been used in several other similar surveys around the world
]. A computerized version has also been developed and found to be comparable with the regular interview
]. The CIS-R assesses the presence and severity of 14 different common psychiatric symptoms during the past 7 days (psychosomatic symptoms, fatigue, concentration/memory problems, sleep problems, irritability, worry about physical health, depressive mood, depressive ideas, general worry, free-floating anxiety, phobias, panic, compulsions and obsessions). Two screening questions in each section ask about the presence of the symptom during the past month and then there is a more detailed assessment of the presence, frequency, duration, and severity of the symptom during the past seven days. Additional questions, including questions assessing the impairment of functioning, enable the diagnosis of six common mental disorders (depressive episode, generalized anxiety disorder, all phobias combined, panic disorder, obsessive compulsive disorder, mixed anxiety and depression disorder) according to the ICD-10 research diagnostic criteria using specially developed computerized algorithms.
The Greek version of the CIS-R has been validated and its psychometric properties have been published elsewhere
]. Each symptom section is scored from 0 to 4 (except depressive ideas from 0 to 5) and a score of 2 or more denotes a clinically significant symptom
]. Using the CIS-R psychiatric morbidity can be assessed either in a dimensional way, using the total score on the CIS-R (by adding-up all 14 symptom dimensions), or in a categorical form using the six diagnostic categories. For the purposes of the present study we have selected to use both in our analyses in order to be able to investigate potential differences between general psychopathology and specific diagnostic categories. For the dimensional assessment, we have defined four groups of severity based on previous work with the UK and Greek samples
]: “no/minimal symptoms” (CIS-R score
0-5), “subthreshold symptoms” (CIS-R score
6-11), “mild symptoms” (CIS-R score
12-17) and “severe symptoms” (CIS-R score
=18). A score on the CIS-R ≥12 (by combining the last two groups into one) is usually considered as the cut-off for “clinically significant” psychiatric morbidity
Assessment of substance use
Alcohol- related disorders were assessed with AUDIT
]. In the present study we used the first three questions in AUDIT (consumption, frequency, binge drinking) to calculate the AUDIT-C subscale with a range of scores from 0 to 12. The AUDIT-C is considered a reliable alcohol screen for use in general population surveys to identify people with hazardous drinking or active alcohol abuse and dependence
]. To define harmful alcohol use we used the cut points suggested by Aalto et al.
] who used data from a general population survey. These were a score of
6 for men and
4 for women. The cut points are different for the two genders as this has been supported by recent research findings on AUDIT
Current smoking status and current (past-month) cannabis use was obtained from the participants by direct questioning. Regarding smoking, participants were asked to report the average number of cigarettes they smoked per day during the past month. A second question asked the participants to classify themselves into one of the following categories: never-smoker, ex-smoker, occasional/light smoker, moderate smoker, heavy smoker. We combined those two questions to define a binary variable of “regular smoker” in the past 30 days (all those who were at least moderate smokers OR reported more than 2 cigarettes per day on average during the past month). Regarding cannabis, we asked two questions, the first for lifetime use (five categories: never, 1–2 times, 3–10 times, >10 times/regular use, do not wish to reply) and the second for past 30 days use (“have you used cannabis during the past 30 days?” with three possible answers: Yes, No, do not wish to reply). We classified participants as users of cannabis during the past 30 days if they replied yes to the second question OR reported regular use to the first.
Assessment of health status
We assessed current health status with the EuroQoL EQ-5D, a generic, preference-based, measure of health-related quality of life
]. This has been validated in Greece by Kontodimopoulos et al.
]. For the purposes of the present paper we calculated the EQ-5D index scores based on responses to the 5-item questionnaire. The scoring algorithm for the EQ-5D index descriptive system used in this paper is based on UK community preferences as analogous preferences are lacking in Greece
]. The mean (SD) value of the EQ index in the present sample was 0.82 (0.23) and was very similar to the value of 0.80 (0.27) reported by Kontodimopoulos et al.
] in their validation study.
Assessment of course and mental health service use
Persistence of illness was assessed by asking the participants to retrospectively assess the duration of their symptoms. Use of mental health services was assessed by asking participants whether they had visited a mental health professional (either a psychiatrist or psychologist) during the past 12 months for any reason concerning their mental health.
Assessment of socio-demographic and other variables
Information about sex, age, marital status, employment status and educational qualifications were obtained from the participants. Regarding employment status, we distinguished between unemployment (i.e. the participant did not do any paid work but looked for any kind of paid work in the past 4 weeks) and economic inactivity (the participant did not do any paid work but did not look for any paid work in the past 4 weeks; additional questions clarified the reason for not seeking any work: a) looking after the house, b) retired, and c) a residual category of “other economically inactive” (including students, persons doing their mandatory military service, those living with parents, those unable to work, living on other income such as rents or shares and other non-specific reasons). Participants were also presented with a list of chronic and severe medical conditions (cardiovascular diseases including coronary heart disease and stroke, chronic lung diseases, diabetes, any malignancy, chronic kidney disease) and asked to report whether they suffered from them.
Data were weighted to account for the complex sampling design and non-response. We used the survey commands in Stata version 10.0 to calculate prevalence estimates and 95% confidence intervals
]. These commands take into account the complex sampling design and compute robust standard errors. Associations between the common mental disorders and sociodemographic associations were examined using odds ratios. These and their 95% confidence intervals were calculated with a series of adjusted logistic regression models using the survey commands in Stata 10.0. All evaluations of statistical significance are based on two-sided tests using the 5% level of significance.