Longitudinal patterns of mental health service utilisation by those with mental-physical comorbidity in the community

Successful healthcare integration demands an understanding of current service utilisation by people with comorbidity. Physical illness may impact on mental health service use (MHSU), but longitudinal studies of comorbidity and MHSU are rare. This study 1) estimated associations between mental-physical comorbidity and longitudinal MHSU patterns; 2) tested whether associations between comorbidity and continuous MHSU are driven by "need".

Survey data from a South East London community cohort were used (N = 1052). Common mental disorder symptoms (CMDS) were measured using the Clinical Interview Schedule Revised and self-report of long-standing disorders. A checklist of common conditions measured chronic physical conditions. MHSU captured self-reported use of mental health services in the past year at two time points. "Need" indicators included CMDS at follow-up, suicidal ideation, somatic symptom severity, self-rated health, daily functioning problems and perceived functioning limitations due to emotional health. Analyses used logistic and multinomial regression.

Continuous MHSU (at both time-points) was twice as commonly reported by those with comorbidity than those without physical comorbidity (30.9% vs 12.3%). CMDS at follow-up, suicidal ideation, and perceived functioning limitations due to emotional health only partially explained the association between CMDS-physical comorbidity and continuous MHSU. In the adjusted model, comorbidity remained associated with continuous MHSU (RRR = 3.23, 95% CI: 1.39-7.51; p = .002), while the association for non-comorbid CMDS was fully attenuated (RRR = 1.08, 95% CI: 0.40-2.93; p = .85).

CMDS-physical comorbidity was strongly associated with continuous MHSU, and "need" did not account for this association, suggesting that comorbidity itself represents a "need" indicator.