Anxiety and depression, chronic physical conditions, and quality of life in an urban population sample study

No previous studies have empirically demonstrated a multiplicative interactive effect of anxiety disorders and/or depression
(ADD) and chronic medical conditions on quality of life (QOL). We hypothesized that QOL impairment was worsened by the presence
of ADD and medical co-morbidity, more than when it was with either medical co-morbidity alone or ADD alone.

Complete data of 2,801 participants from the National Mental Health Survey of Adults in Singapore were analyzed, using SCAN
diagnoses of anxiety disorders and depression, self-reports of chronic medical conditions, and SF-12 measures of QOL (Mental
Component Summary, MCS, and Physical Component Summary, PCS).

Persons diagnosed with ADD (compared to those without) had considerably more medical co-morbidities (59 vs. 33%, p < 0.001). In multiple regression analyses, ADD (vs. no ADD) was associated with lower PCS (b = −1.013, p = 0.045) and MCS scores (b = −9.912, p < 0.001), as was number of medical co-morbidities (0, 1–2, 3 +), PCS scores (b = −2.058, p < 0.001) and MCS scores (b = −1.138, p < 0.001). There were significant interactive effects of medical co-morbidities and ADD on PCS (p < 0.001), and MCS (p = 0.086), suggesting that the negative effects of medical conditions on quality of life was aggravated non-additively by
the co-morbid presence of ADD, and vice versa.

The individual effects of medical and psychiatric morbidity on functional status and quality of life were considerably worse
when both were present in the same individual. Future studies should examine the impact of identifying and treating anxiety
and depressive disorders in patients with medical problems for better outcomes.