The association between autistic traits and trajectories of anxiety in middle-aged and older adults: an 8-year growth mixture model analysis.

Anxiety is a highly prevalent mental health condition, and it is particularly common in autistic populations. However, little is known about its course beyond midlife in autistic populations owing to limited longitudinal research. Here we analyzed data from 5,270 adults aged 50-91 years (median 62 years; 75% female) in the PROTECT study. Participants completed measures of autistic traits (the Autistic Spectrum Traits Questionnaire) and current anxiety symptoms (the Generalized Anxiety Disorder-7 questionnaire). In total, 66 participants (~1.3%; 72.3% female) had high autistic traits (AST group), while 3,874 (~73.5%; 77.8% female) reported none (comparison adults). Growth mixture modeling identified anxiety symptom trajectories over an 8-year annual follow-up period. Associations between AST group and trajectory membership were examined using multinomial logistic regression. Growth mixture modeling revealed three class trajectories: two representing persistently minimal anxiety symptoms (class 1, 'lower range minimal', 85.6% of sample; class 2, 'upper-range minimal', 12.4% of sample) and one showing rising anxiety from 'mild to clinical' levels (class 3, 2% of sample). Regressions showed that AST participants were more likely than comparison adults to follow the mild-to-clinical trajectory (relative risk 4.41, 95% confidence interval 1.70-11.44). Elevated autistic traits are associated with an increased risk of worsening anxiety with age, highlighting the need for tailored support.