The selection of risk factors for the onset and persistence of depression was designed to cover all important areas identified in a systematic review of the literature, considering specially those assessed in the predictD international study [
26], in addition to other possible professional and organizational risk factors. Where possible, we used published measures with established reliability and international validity, including in Spain. Where this was not possible we translated the measures into Spanish. Each translation was back-translated by professional translators. In some cases, questions were developed for the study or adapted from available standardised instruments. These questions were evaluated for test-retest reliability. Scales without validation data in Spain were also evaluated on their internal consistency and factorial validity.
Individual and environmental risk factors
• Socio-demographic factors: age, marital status, occupation, employment status, ethnicity, nationality, country of birth, educational level, income, owner occupier accommodation, living alone or with others.
• Controls, demands and rewards for unpaid and paid work, using an adapted version of the job content instrument [
50].
• Debt and financial strain [
9].
• Consultation rate in the general practice through computerized clinical notes [
51].
• Physical and mental well-being, assessed by the SF-12 that has application across a number of cultures [
52], including Spain [
53]; and a question on the presence of long-standing illness, disability or infirmity.
• Alcohol abuse using the WHO AUDIT questionnaire [
54], the Spanish validation of which slightly modified the threshold for female hazardous drinkers [
55,
56].
• Use of recreational drugs (at least once in the past and over the previous six months) adapted from the relevant sections of the CIDI.
• A life-time screen for depression based on the first two questions of the CIDI. People answering yes to both questions screened positive [
57].
• Brief questions on cigarette consumption.
• For women, questions on menstruation, pregnancy and childbirth from the Patient Health Questionnaire (PHQ) [
58].
• Brief questions on the quality of sexual and emotional relationships with a partner, adapted from a standardized questionnaire [
59].
• Presence of serious physical, psychological or substance misuse problems, or any serious disability, in persons who are close friends or relations of participants; and difficulty getting on with people and maintaining close relationships, assessed using questions from a social functioning scale [
60].
• Childhood experiences of physical, emotional or sexual abuse [
61].
• Nature and strength of spiritual beliefs [
62].
• Family psychiatric history in first-degree family members requiring pharmacological or psychological treatment in primary or secondary care, and suicide in first-degree relatives [
63].
• Anxiety symptoms using the anxiety section of the PRIME-MD [
58]. The Spanish version provides psychiatric diagnoses according to DSM-IV: Panic Attack, Generalised Anxiety Disorder and Other Anxiety Disorders [
64].
• One question on whether and when (at what age) the participant had lost one or both parents by death.
• Household type and composition.
• The living environment, including satisfaction with neighbourhood and perception of safety inside/outside the home using questions from the Health Surveys for England [
65].
• Recent life-threatening events, using a brief validated checklist [
66].
• Experience of discrimination on the grounds of sex, age, ethnicity, appearance, disability or sexual orientation using questions from a recent European study [
67].
• Adequacy, availability and sources of social support from family and friends [
68].
Professional and organizational risk factors
This group of variables will be gathered from computerised clinical notes, centralised administrative records, and a brief questionnaire to the GPs at 12, 24 and 36 months.
• GP characteristics: age, gender, year of degree in Medicine, postgraduate training and speciality, type of contract, time in the current health centre, list size, mean time per patient during the previous year, satisfaction with relationships and collaborative care between GP and mental health team, social worker, and nurse practitioner, self-perceived comfort with antidepressant use, and a questionnaire on professional satisfaction, perception of workload, and psychosocial orientation [
69].
• Health Centre characteristics: size of population attended, number of inhabitants in the city or town, predominant activity in the city or town (agriculture-fishing, industry or services), number and type of professionals in the team, professional-population ratios, type and intensity of relationship with Mental Health team (case management, patient care and shared continued medical education), and "centred variables" (mean or median of the GP characteristics in each health centre).
• Interaction professional-organization-patient variables: number of visits to health centre team, i.e., GP, nurse, and social worker; referrals to the Mental Health team by GPs or direct approaches to mental health specialists by the patient privately; patient's psychosocial and physical problems detected by their GPs; and antidepressants, benzodiazepines or other psychological drugs prescribed (type, dose and duration).