Longitudinal changes in cognitive and adaptive behavior scores in children and adolescents with the fragile X mutation or autism.

Jaffe et al. (2002) tracked the same kids for several years. They measured IQ and daily living skills in two groups: children with fragile X and children with autism.

The team wanted to see if these scores rose, held steady, or dropped as the kids grew older.

Both groups lost ground. IQ and adaptive behavior slid downward over time. The fragile X drop was steeper, especially in IQ.

Kids with autism also declined, but at a slower pace.

Boudreau et al. (2015) later looked at fragile X teens and found a split picture: verbal IQ went up while non-verbal IQ went down. That finer detail extends the current study by showing not every cognitive skill falls.

Fujiura et al. (2018) saw a similar adaptive-behavior plateau in autism-only kids, giving a conceptual replication of the decline reported here.

Olsson et al. (2001) studied younger fragile X boys and linked autistic behavior—not gene protein level—to slower growth. Their earlier data foreshadowed the steep IQ slide S et al. later confirmed.

Expect long-term losses in both cognition and daily skills for clients with autism or fragile X. Plan goals that maintain rather than just increase skills. Start self-care, communication, and academic routines early and keep them running through adolescence. Re-assess often; if verbal scores hold while non-verbal fall, adjust teaching methods and parent expectations accordingly.