The association between chronic illness, multimorbidity and depressive symptoms in an Australian primary care cohort

Purpose To assess the link between multimorbidity, type of chronic physical health problems and depressive symptoms Method The study was a cross-sectional postal survey conducted in 30 General Practices in Victoria, Australia as part of the diamond longitudinal study. Participants included 7,620 primary care attendees; 66% were females; age range from 18 to 76 years (mean = 51years SD = 14); 81% were born in Australia; 64% were married and 67% lived in an urban area. The main outcome measures include the Centre for Epidemiologic Studies Depression Scale (CES-D) and a study-specific self-report check list of 12 common chronic physical health problems. Results The prevalence of probable depression increased with increasing number of chronic physical conditions (1 condition: 23%; 2 conditions: 27%; 3 conditions: 30%; 4 conditions: 31%; 5 or more conditions: 41%). Only 16% of those with no listed physical conditions recorded CES-D scores of 16 or above. Across the listed physical conditions the prevalence of ‘probable depression’ ranged from 24% for hypertension; 35% for emphysema; 35% for dermatitis to 36% for stroke. The dose–response relationship is reduced when functional limitations and self-rated health are taken into account, suggesting that these factors mediate the relationship. Conclusions A clear dose–response relationship exists between the number of chronic physical problems and depressive symptoms. The relationship between multimorbidity and depression appears to be mediated via self-perceived health related quality of life. Primary care practitioners will identify more cases of depression if they focus on those with more than one chronic health problem, no matter what the problems may be, being especially aware in the group who rate their health as poor/fair.