PDD-NOS symptoms in adults with intellectual disability: toward an empirically oriented diagnostic model.

Matson et al. (2008) watched and recorded real PDD-NOS signs in adults who already had intellectual disability.

They wrote down which behaviors showed up most often. No treatment was tested; they simply mapped the symptoms.

The team produced a clear list of PDD-NOS features seen in this adult ID group.

These real-world observations give future clinicians something solid to check against during evaluations.

Matson et al. (2008) asked a follow-up question one year later: do these same adults also differ in everyday adaptive skills? They found that adding ASD lowered Vineland scores, so diagnosis and daily ability are linked.

Busch et al. (2010) looked at adults with ID plus both ASD and epilepsy. They saw more anxiety, irritability, ADHD, and depression than in groups with only one extra diagnosis. Together with Matson et al. (2008), the picture is clear: each extra condition brings its own symptom layer.

Keel et al. (1997) had earlier argued that we need standard rules for spotting dementia in adults with ID. Matson et al. (2008) used the same idea—empirical lists—but aimed it at PDD-NOS instead of dementia, moving the field from opinion to evidence.

If you assess adults with ID, you now have an evidence-based checklist for PDD-NOS. Use it to avoid under-diagnosing or over-diagnosing autism traits in this population. Pair it with adaptive data from Matson et al. (2009) and psychopathology screens from Busch et al. (2010) to build a full support plan.