We examined long-term outcomes of attention-deficit/hyperactivity disorder (ADHD) in a population-based sample of childhood ADHD cases and controls, prospectively assessed as adults.
Adults with childhood ADHD and non-ADHD controls from the same birth cohort (N = 5718) were invited to participate in a prospective outcome study. Vital status was determined for birth cohort members. Standardized mortality ratios (SMRs) were constructed to compare overall and cause-specific mortality between childhood ADHD cases and controls. Incarceration status was determined for childhood ADHD cases. A standardized neuropsychiatric interview was administered.
Vital status for 367 childhood ADHD cases was determined: 7 (1.9%) were deceased, and 10 (2.7%) were currently incarcerated. The SMR for overall survival of childhood ADHD cases versus controls was 1.88 (95% confidence interval [CI], 0.83–4.26; P = .13) and for accidents only was 1.70 (95% CI, 0.49–5.97; P = .41). However, the cause-specific mortality for suicide only was significantly higher among ADHD cases (SMR, 4.83; 95% CI, 1.14–20.46; P = .032). Among the childhood ADHD cases participating in the prospective assessment (N = 232; mean age, 27.0 years), ADHD persisted into adulthood for 29.3% (95% CI, 23.5–35.2). Participating childhood ADHD cases were more likely than controls (N = 335; mean age, 28.6 years) to have ≥1 other psychiatric disorder (56.9% vs 34.9%; odds ratio, 2.6; 95% CI, 1.8–3.8; P < .01).
Childhood ADHD is a chronic health problem, with significant risk for mortality, persistence of ADHD, and long-term morbidity in adulthood.
Comments
In Response to " Mortality, ADHD, and Psychosocial Adversity in Adults With Childhood ADHD: A Prospective Study"
To the Editors,
It was with great interest that I read "Mortality, ADHD, and Psychosocial Adversity in Adults With Childhood ADHD: A Prospective Study", which addresses the clinically relevant topic of long-term outcomes of childhood ADHD. Some of the study's strengths include the use of data from a population-based sample that was followed prospectively into adulthood and access to a rich source of medical and educational record data to identify the ADHD incident cases and examine the outcomes of interest.
However, there are several limitations to the study design and conclusions that warrant mention. While criteria to identify the childhood ADHD cases were described, the authors subsequently describe the identification of 5 additional cases based on self-report that were then reclassified as cases instead of controls. The authors do not describe a systematic method for identifying additional childhood ADHD cases among the controls, raising the question of the extent to which differential misclassification of the incident cases may have influenced the reported outcome estimates. Additionally, there is a lack of information on the characteristics of non-ADHD control group. This is particularly important given that the classification of adult ADHD was based on the distribution of self-reported symptoms and degree of impairment endorsed by the non- ADHD control group.
The article's discussion seems to overstate the study's main findings and inadequately address its limitations. The authors state that the study "confirms" that having childhood ADHD is associated with an increased risk of early death from suicide. While the reported risk was increased, it was calculated on a small number of deaths and the width of the odds ratio confidence interval calls into question the precision of the reported estimate. Also, the cumulative burden of ADHD in the form of "social adversity in the form of criminal behavior" was included in the discussion section list of findings. However, an association between childhood ADHD and criminal behavior was not examined in the study because incarcerated cases were excluded from the study and data on incarcerated controls was not available.
The impact of childhood ADHD on future adult functioning is one of the very first things parents ask about when a child is diagnosed with ADHD, so the authors' findings have important implications for counseling parents. Given its limitations however, the study's findings are suggestive of several increased risks conferred by a childhood diagnosis of ADHD, but are far less definitive than suggested. They should be interpreted with caution and parents should be counseled accordingly.
Elisa I. Muniz, MD
Conflict of Interest:
None declared