This cross-sectional study was conducted in Family Health Care's field of Ribeirão Preto city, São Paulo, Brazil to identify the prevalence of substance-related disorders and mental distress among patients with mental disorders. We also aimed to identify sociodemographic and social support risk factors. The data collection was done using medical records, the Social Support Questionnaire (SSQ-6), Self Report Questionnaire (SRQ-20) and home visits. Of the 272 families studied, 211 contained individuals with mental disorders, and 61 included individuals who had substance-related disorders, or both. The mental disorders recorded in these families were most frequently mood disorders, followed by neurotic disorders, stress-related disorders and somatoform disorders. Women received twice as many psychotropic prescriptions associated with non-psychiatric medication. A significant relationship was established between education and mental distress as measured using the SRQ-20 (p = 0.024). The SSQ-6 revealed a family presence of social support in all of the conditions established by the six questions.