Prevalence of Depression in the General Population of Latvia and Primary Care Sample in Riga and Riga District. Summary of the Doctoral Thesis

Abstract

Background. Depression is one among the most common mental disorders in European general population. The WHO prognoses that by 2020 depression will be a second leading disorder in terms of disability adjusted life years. Despite rich data on depression prevalence rates in European countries, no population-based studies of the prevalence of depression and associated factors have been conducted in Latvia. The aim of the doctoral thesis was to determine the prevalence of depression, associated sociodemographic and health-related factors, as well as to determine the prevalence of depression of the primary care patients in Riga and Riga district and to validate a depression screening tool in primary care sample. Material and methods. The study was conducted in three consecutive sections. First, the point prevalence of depression and associated sociodemographic correlates in the general population was estimated in a cross-sectional general population survey on substance use in Latvia in 2011 with a total sample of 4493 Latvian inhabitants. Sociodemographic, self-rated health status, alcohol use measures, and data about depression were evaluated from the structured face-to-face interviews. To assess depression, participants were interviewed using the Patient Health Questionnaire-9 (PHQ-9) with a cut-off score of ≥ 10. Logistic regression models were applied to the data. Model 1 was adjusted only by gender and age, Model 2 was adjusted by all simultaneous factors. Second, the 12-month prevalence of depression, “minor depression” and associated health related factors was determined in the study that was a part of the Health Behaviour among the Latvian Adult Population survey in 2012 with a total population of 3003. Data was collected by face-to-face interviews. In order to measure depression and minor depression, the participants were interviewed using the depressive episode module of the Mini International Neuropsychiatric Interview (M.I.N.I.). Multinomial logistic regression was used because the dependent variable (depression status) had more than two categories. Third, in 2014, a pilot study was conducted within the framework of the Latvian National Research Programme BIOMEDICINE (2014–2017) to assess the prevalence of depression in primary care sample at 6 primary care settings and to estimate the PHQ-9 cutoff score with the best sensitivity, specificity, Criterion validity was assessed against the M.I.N.I. The criterion validity of the PHQ-9 was analyzed in terms of sensitivity, specificity, and positive and negative predictive values for different cutoff scores. Results. The point prevalence of depression in the general population was 6.7%. Depression was more common in females (7.8%, 95%CI6.2%–9.5%) than males (5.6%, 95%CI4.2%–6.9%). The odds of having depression were higher in females, in urban dwellers (though not in the capital city, Riga), in persons with alcohol dependence, with poor subjective health status and having a dissatisfaction with life. The 12-month prevalence of major depression was 7.9%, while for minor depression it was 7.7%. The prevalence of self-reported somatic illnesses was higher among people with depression and minor depression than in people with no depression. The odds of having 12-month depression were higher for those who had used healthcare services six or more times, those who had three or more somatic disorders during the past 12 months, those who perceived their health status as being below average, and those who were regular and occasional smokers. The odds of having minor depression was increased for those who had at least three somatic disorders, those who received disability pension, and those who perceived their health status to be below average. In primary care setting 22.4% of patients had experienced a lifetime depression episode, and 13.6% of patients had current depression. A cutoff score of 10 was established for the PHQ-9 (sensitivity 0.86, specificity 0.89%), correctly classifying 86.4% of patients with current depression. The reliability analysis showed that the items of the PHQ-9 were highly consistent (Cronbach’s alpha 0.83). Conclusions. Certain socio-demographic and health-related factors associated with depression and minor depression have been identified. The findings outline certain individuals who might be at a higher risk of having depression. The factors associated with major or minor depression could be used as indicators for health providers to initiate screening for depression. The optimal cut-off score of the PHQ-9 that had the best psychometric characteristics for diagnosing depression was ≥10. The study demonstrates that the PHQ-9 is a reliable and effective instrument to evaluate depression among patients visiting their general practitioner in Latvia.