Sick leave in young adults diagnosed with childhood ADHD and references, a prospective cohort study

Background

Most studies on sickness absence (SA) and attention-deficit hyperactivity disorder (ADHD) are based on adults, irrespective of individual age at diagnosis.

Purpose

To explore future SA (in SA spells >14 days) and disability pension (DP) in young adults who were diagnosed with ADHD in childhood.

Methods

A prospective cohort study using microdata linked from 5 Swedish nationwide registers of the 62,910 people born in 1973-2001 diagnosed with ADHD when aged 4-17 and 1:8 references (n = 503,280) matched on sex and birth year, without childhood ADHD. Group‑based trajectory modelling was used to identify patterns of SADP days/year among those 7768 in the ADHD cohort and their 62,179 matched references who could be followed over 12-years (e.g., when aged 18-29). Multinominal logistic regression was used to estimate odds ratios (OR) of associations between individual factors and trajectory memberships.

Results

Young adults with childhood ADHD, especially women, had substantially higher SA and DP levels compared with matched references. In the 12-year follow-up, 6 SADP trajectories were identified among women with childhood ADHD: (1) ‘Low, constant’ (38.4% of all), (2) ‘Low, increasing some’ (13.3%), (3) ‘Low, increasing much’ (7.6%), (4) ‘Some, decreasing much’ (7.6%), (5) ‘Some and fluctuating’ (7.6%), and (6) ‘Some, increasing much’ (25.6%). Four of these trajectories were identified among men with childhood ADHD; 1) ‘Low, constant’ (57.1%), 2)’ Low, increasing some’ (8.7%), 4) ‘Some, decreasing much’ (24.2%), and 6) ‘Some, increasing much’ (24.2%). Among women with childhood ADHD, also diagnosed with childhood autism, the OR of belonging to 6) ‘Some, increasing much’ trajectory was 5.0 (95%CI 3.4-7.6). The corresponding OR for those men was 6.1 (95%CI 5.0-7.6).

Conclusions

Childhood ADHD was associated with significantly elevated and heterogeneous long‑term SADP patterns in young adulthood, with substantial sex differences. Autism increased the ORs of high SADP levels.

Key messages

• About 50% of women and 66% of men with childhood ADHD had trajectories of low levels or no sick-leave/disability pension during the 12-year follow-up, while about 25% had much increasing levels.

• Having both childhood ADHD and autism was associated with high and heterogenous SADP levels both in women and men. Knowledge is needed on how to support their future study- and work participation.