BackgroundPoor mental health is known to adversely affect functional abilities, social isolation, and quality of life. It is, therefore, crucial to consider the long-term impacts of mental health conditions as autistic adults grow older.ObjectivesTo explore, in a group of community-based autistic adults, the extent of: autistic traits, co-occurring physical and mental health conditions; age-related differences in those conditions, and changes over time; and their impact on everyday living and QoL.MethodAbout Sixty-eight autistic adults participated in the first study ; 49 participants (...) from T1 took part in a follow-up at T2. Standardised self-report measures of autistic traits, mental health, and QoL were completed at both time points.ResultsOver two-thirds of autistic adult participants experienced at least one co-occurring condition, and over a third met the criteria for three or more co-occurring conditions. Mental and physical health difficulties were related to autistic traits and difficulties in everyday life and were consistent predictors of poor QoL at T1 and T2.ConclusionMental health difficulties in autism persisted into older age and did not improve over time. These findings have important implications for mental health provision for autistic adults in older age. (shrink)