Einfeld et al. Psychopathology in young people with intellectual disability. JAMA. 2006 Oct 25;296(16):1981-9.:It's a dense and not very readable article. I couldn't figure out what "normal" children score on their developmental behaviour checklist; there's no control group in this study. They did say a score of 46 was definitely pathologic, so the mean score starting out was just below that. Boys started out a bit worse than girls and ended up slightly better, but you have to squint to see the difference. I doubt it means all that much.
CONTEXT: Comorbid severe mental health problems complicating intellectual disability are a common and costly public health problem. Although these problems are known to begin in early childhood, little is known of how they evolve over time or whether they continue into adulthood.
... MAIN OUTCOME MEASURES: The Developmental Behaviour Checklist (DBC), a validated measure of psychopathology in young people with intellectual disability, completed by parents or other caregivers. Changes over time in the Total Behaviour Problem Score and 5 subscale scores of the DBC scores were modeled using growth curve analysis. ...
RESULTS: High initial levels of behavioral and emotional disturbance decreased only slowly over time, remaining high into young adulthood, declining by 1.05 per year on the DBC Total Behaviour Problem Score. Overall severity of psychopathology was similar across mild to severe ranges of intellectual disability (with mean Total Behaviour Problem Scores of approximately 44).
Psychopathology decreased more in boys than girls over time (boys starting with scores 2.61 points higher at baseline and ending with scores 2.57 points lower at wave 4), and more so in participants with mild intellectual disability compared with those with severe or profound intellectual disability who diverged from having scores 0.53 points lower at study commencement increasing to a difference of 6.98 points below severely affected children by wave 4. This trend was observed in each of the subscales, except the social-relating disturbance subscale, which increased over time. Prevalence of participants meeting criteria for major psychopathology or definite psychiatric disorder decreased from 41% at wave 1 to 31% at wave 4. Few of the participants (10%) with psychopathology received mental health interventions during the study period.
I found the negative spin of the article a bit odd. Did anyone really expect that these behavioral disorders would completely resolve? I thought it was quite encouraging that a quarter of children who started out with a psychicatric disorder ended up without one - despite what appeared to be few mental health interventions. The low rate of intervention is remarkable, I wonder if it's any different in the US?
So the bottom line? Boys seem to improve more, but boys and girls don't end up that differently. Without much mental health intervention there's still very significant improvement over 10 years or so. We might do much better with half-decent pychiatric services, but that is not proven (Personally I would bet on it).