In this study from the Schizophrenia Research journal, the researchers compared two groups of adults with schizophrenia - those whose illness began before age 19 (early onset) and those whose illness began at age 19 or later (adult onset) - and measured their current IQ as well as an estimate of what their IQ was before the illness took hold.
The findings reflected that adults with early onset schizophrenia scored about 5 IQ points lower across the board than those with adult onset. The gap shows not where someone started, but how far they fell - both groups had similar estimated IQ levels before their illness began. In other words, early onset patients did not appear to start life with lower cognitive ability. Instead, they experienced a steeper decline after onset - roughly 11 IQ points lost on average, compared to about 8 for the adult onset group.
Why might this be? The researchers suggest it has to do with timing. When schizophrenia emerges during adolescence, it disrupts a brain that is still actively developing. The illness may interfere with critical windows of cognitive growth that, once missed, are difficult or impossible to recover. Adult onset patients, by contrast, have had more time for their cognitive foundations to solidify before the illness arrives.
This has real implications. Early onset schizophrenia is already associated with a more difficult prognosis — more severe symptoms, greater functional impairment, and longer periods of untreated illness that overlap with school, social development, and early adulthood. The cognitive decline identified in this study may help explain some of that harder trajectory.
Importantly, standard antipsychotic medications, while effective at managing positive symptoms like hallucinations and delusions, do little to address cognitive deficits. The authors point to cognitive remediation as a promising avenue, and note that such interventions have shown benefits in both adolescents and adults with schizophrenia.
The study is not without limitations. Because it looked at patients at a single point in time rather than following them across years, it cannot pinpoint exactly when the cognitive decline happens or how quickly it progresses. Longitudinal research tracking patients from onset through adulthood would offer a clearer picture.
Still, the core message is worth sitting with: for those who develop schizophrenia early in life, the illness may be doing more cognitive damage than we previously appreciated - and the window for intervention matters.