This systematic review covered 351 studies published between 1980 and 2010. They gave 636 outcome results across nine areas of life. Participants had diagnosed or symptomatic ADHD, from children to adults. Studies followed people for an average of 9 years, ranging from 2 to 40. Treatment meant drugs, non drug approaches or a mix.
Untreated ADHD went with poorer outcomes than people without ADHD in 74% of the outcome results. The rest were counted as similar, although six were in fact significantly better than controls.
One smaller set compared treated with untreated ADHD, in 48 studies giving 76 outcome results. Treatment looked favorable for 55 of those. Counting all 76, improvements against an untreated group made up 38%. Improvements against a person's own pretreatment baseline made up 22%. Stabilization against baseline made up another 12%, and the authors note those studies had no untreated group. No difference against an untreated group was reported for 25%. Two single outcomes were worse: experimenting with cocaine, against untreated ADHD, and falling grade point average, against baseline.
A separate set of 42 studies compared treated ADHD with people without ADHD, again with 76 outcome results. Treatment rarely closed the gap. Outcomes stayed poorer in 58 of those results, from 35 studies.
Results were sorted into categories rather than pooled, and many studies reported no effect size. A natural decline in symptoms over time cannot be ruled out.
Anyone weighing what this means for their own situation should talk with a clinician.
Source: Monica Shaw, Paul Hodgkins, Hervé Caci, et al.. A systematic review and analysis of long-term outcomes in attention deficit hyperactivity disorder: effects of treatment and non-treatment. BMC Medicine (2012). doi:10.1186/1741-7015-10-99