Behavioural strengths and difficulties in relation to intellectual functions and age in Swedish boys with Duchenne muscular dystrophy.

The aim of this study was to describe behavioral strengths and difficulties in relation to intellectual function and age in boys with DMD. In a cross-sectional design, 70 boys with DMD were tested at 5, 8, 11, and 14 years of age (mean age 10y 5 m). Parental ratings of behavioral strengths and difficulties were studied in relation to age, intellectual function, motor function, and family socioeconomic status (SES). Results show a significant relation between behavioral strengths and difficulties and age with parents rating increasingly more difficulties (slightly higher, higher and very high) from 5 years (11.1%) to 9 years (30.8%) and 11 years (78.9%) of age and then fewer difficulties at 14 years (50%) of age. Working Memory Index (WMI) explained significant variance in SDQ-Total-Score (17.5%) and SDQ-Impact-Score (11.2%). WMI together with upper motor function explained 19.5% variance in SDQ-Hyperactivity and 19.7% in SDQ-Peer-Problems. Age and SES explained an 18.9% variance in SDQ-Emotional-Problems. Age is an important factor when analyzing behavioral strengths and difficulties for boys with DMD. The development of boys with DMD needs to be understood in the context of expected developmental trajectory as well as in the decline of psychical functioning. Our study supports that age, cognition, motor function, and family SES all contribute to how behavioral strengths and difficulties evolves in boys with DMD.