Comorbidity within mental disorders: a comprehensive analysis based on 145 990 survey respondents from 27 countries

Abstract

Aims Epidemiological studies indicate that individuals with one type of mental disorder have an increased risk of subsequently developing other types of mental disorders. This study aimed to undertake a comprehensive analysis of pair-wise lifetime comorbidity across a range of common mental disorders based on a diverse range of population-based surveys. Methods The WHO World Mental Health (WMH) surveys assessed 145 990 adult respondents from 27 countries. Based on retrospectively-reported age-of-onset for 24 DSM-IV mental disorders, associations were examined between all 548 logically possible temporally-ordered disorder pairs. Overall and time-dependent hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox proportional hazards models. Absolute risks were estimated using the product-limit method. Estimates were generated separately for men and women. Results Each prior lifetime mental disorder was associated with an increased risk of subsequent first onset of each other disorder. The median HR was 12.1 (mean = 14.4; range 5.2–110.8, interquartile range = 6.0–19.4). The HRs were most prominent between closely-related mental disorder types and in the first 1–2 years after the onset of the prior disorder. Although HRs declined with time since prior disorder, significantly elevated risk of subsequent comorbidity persisted for at least 15 years. Appreciable absolute risks of secondary disorders were found over time for many pairs. Conclusions Survey data from a range of sites confirms that comorbidity between mental disorders is common. Understanding the risks of temporally secondary disorders may help design practical programs for primary prevention of secondary disorders.

Co‐morbidity between mood and anxiety disorders: A systematic review and meta‐analysis

“…In some disorder pairs (e.g., MOOD and GAD), the pooled estimate was as high as 19 times (aOR = 18.7). However, our estimates were broadly consistent with two studies that were published after the completion of our data extraction: a large register‐based study from Denmark ( n = 5 940 778) (Plana‐Ripoll et al, 2019), and a trans‐national analysis that combined individual data from 27 countries ( n = 145 990 survey respondents) (McGrath et al, 2020). Overall, the consistent patterns identified by our systematic review, and the findings from these two recent studies, provide convergent evidence of the strong comorbidity between these disorders.…”

“…However, these estimates were based on a limited number of studies. Although this bidirectional association was broadly consistent with our recently conducted population‐based studies (McGrath et al, 2020; Plana‐Ripoll et al, 2019), there was a lack of consistency between these studies regarding the symmetry between the size of the reciprocal risk estimates (i.e., did the effect sizes differ according to order, regardless of the fact that both estimates were substantially above 1 and significant). Bi‐directionality within pairs of comorbid disorders suggests that these disorders may result from shared underlying risk factors (e.g., genetic; Levey et al, 2020; Purves et al, 2019; and/or shared early life exposures; Kessler et al, 1997).…”

“…A recent large Danish register‐based study ( n = 5 940 778) found that those who developed a mood disorder by age 20 had a four‐fold risk of subsequently developing an anxiety disorder (OR = 4.3; 95% CI = 4.1–4.4) (Plana‐Ripoll et al, 2019). An analysis of community‐based surveys from 27 countries also showed a very high rate of comorbidity between mood and anxiety disorders; the risk of developing generalized anxiety disorder was about seven times in those with major depression even after 15 years (hazard ratio = 6.6; 95% CI = 5.7–7.7) (McGrath et al, 2020).…”

Brief Research Report: A Pilot Study of Cognitive Behavioral Regulation Therapy (CBT-REG) for Young People at High Risk of Early Transition to Bipolar Disorders

“…In this pilot study of a small case series, we found evidence that about 21% could be viewed as having a poor clinical outcome with 7% of participants (one individual) developing BD, 7% a psychotic disorder, and 7% continuing to experience mood problems, but without transition to full-threshold BD (or perhaps transition has been delayed). It is recognized that individuals who do not show transition from subthreshold to full-threshold disorders are not necessarily well, and many continue to experience a range of clinical and social impairments ( 4 , 6 , 7 ). As such, it is encouraging that 43% of the case series (six individuals) were known to be well enough to be fully discharged from mental health care.…”

“…To date, most interventions have been “disorder-specific” aiming to reduce or delay onsets of full-threshold episodes of a particular diagnosis. However, it is debatable whether a pure “disorder-specific” strategy is the best option as longitudinal and concurrent comorbidity among psychotic and mood disorders is the rule rather than the exception in youth ( 2 ) and those with onsets by age 20 have the greatest risk of developing other mental disorders over the following 15 years ( 3 , 4 ). Furthermore, subthreshold psychotic, depressive or bipolar syndromes show both homotypic continuity (continuity to the full-threshold disorder most similar to the subthreshold condition) and heterotypic continuity (transition to a different full-threshold disorder) ( 5 ).…”