Simplex and multiplex stratification in ASD and ADHD families: a promising approach for identifying overlapping and unique underpinnings of ASD and ADHD?

The team sorted autism families into two buckets. Single-incidence (SPX) means one child has ASD. Multiplex (MPX) means two or more children have ASD or ADHD.

They then counted sub-clinical traits in parents and siblings. The goal was to see if MPX families carry extra ASD-ADHD features that SPX families do not.

MPX families showed higher rates of social-communication quirks, attention problems, and rigid routines in relatives. SPX families looked almost like typical families on these measures.

The pattern held for both ASD and ADHD traits. This suggests the two disorders may share some family-level risk factors.

Fahmie et al. (2013) saw the same SPX-MPX split two years earlier, but only for ASD traits. The new paper adds ADHD traits and confirms the divide still stands.

Bora et al. (2017) used math instead of family structure. They carved ASD parents into high- and low-trait groups with a questionnaire. Both methods spot heterogeneity, but SPX-MPX is faster in clinic—you just count affected kids.

Allen-Brady et al. (2010) took a genetic route. They pulled out high-risk AGRE pedigrees and found a hint of an autism gene on the X chromosome. The current study gives clinicians a simple behavioral rule—MPX status—to pick families likely to carry shared risk without any blood draw.

When you intake a new client, ask how many siblings have ASD or ADHD. If the answer is two or more, expect broader trait loads in parents and plan for possible attention or rigidity issues during sessions. This quick label can guide goal choice, parent training topics, and even sibling screening.