Subthreshold psychiatric disorders in primary care: prevalence and associated characteristics

The authors analyse the prevalence of subthreshold psychiatric disorders in primary care and their association with the patient's health perception, disability in daily activities and psychological distress.

Five-hundred and fifty-four primary care patients who completed a two-phase study were administered the Composite International Interview for Primary Health Care (CIDI-PHC) and other self-report measures. Unweighted and weighted prevalence estimates were obtained for ICD-10 formal disorders and subthreshold disorders defined by specific operational criteria. The impact of subthreshold disorders on health perception, disability in daily activities and psychological distress was analysed by using multiple regression models.

The overall prevalence of subthreshold disorders exceeded that of ICD-10 disorders. Subjects with subthreshold disorders reported levels of psychological distress, disability in daily activities and perceived health comparable to those of patients with full-fledged ICD-10 disorders. When we analysed the associated health characteristics of individual subthreshold disorders, we found that each subthreshold disorder was characterized by poorer health perception, after adjusting for comorbidity with defined disorders and physical illness, age and gender. Disability in daily activities was increased in individuals with subthreshold depression and agoraphobia.

The number of cases with subthreshold panic and somatization is very small and does not allow one to draw any definite conclusions on their associated characteristics. To reduce non-response bias related to sampling design and refusals, adjusted sampling weights were computed. Since the study design in Bologna and Verona was different and Bologna patients scoring <4 on the General Health Questionnaire were not interviewed, individuals with minimal distress come from the Verona sample alone.

Because of the prevalence and associated characteristics of subthreshold disorders, primary care physicians should attach adequate importance to the patient's perceived poor health, distress and inability to fulfil daily tasks. The clinical relevance of subthreshold disorders has also potential implications for ongoing revisions of classification systems.