Title: Trajectories of Hyperactivity and Inattention Symptom Scores in Boys of Low Socioeconomic Status
Description: Attention-deficit hyperactivity disorder (ADHD), once considered a childhood-limited neuropsychiatric condition, is now recognized as often persisting into adolescence and beyond. Recent studies of ADHD and its symptom domains--hyperactivity and inattention--indicate that symptoms can wax and wane over time and follow discrete trajectories characterized by different symptom levels and shapes. However, little is known about symptom trajectories in high-risk groups, such as boys from low socioeconomic backgrounds. Childhood ADHD is associated with cigarette smoking in adolescence, but whether the risk is specific to hyperactivity or inattention or their respective symptom trajectories is not clear. The aims of my dissertation research were to identify trajectories of hyperactivity and inattention symptom scores in a sample of boys from low socioeconomic backgrounds and to assess the associations of those trajectories with cigarette smoking outcomes in late adolescence and young adulthood.

In pursuit of those aims, I first conducted a narrative literature review to assess current evidence regarding the persistence of childhood ADHD, hyperactivity and inattention into adolescence, and the associations of persistent ADHD and its symptom domains with the risks of cigarette smoking and nicotine abuse and dependence in adolescence and early adulthood. Data on boys of low socioeconomic status, where available, were summarized. Evidence suggests that nearly 50% of individuals with childhood ADHD or its symptom domains continue to have symptoms in adulthood. Hyperactivity symptom trajectories are likely to decline over time, whereas inattention symptom trajectories are more stable. The sparse literature on the association between ADHD, hyperactivity, and inattention symptom persistence and high symptom score trajectories and smoking outcomes suggests that high inattention symptom score trajectories are associated with earlier onset and higher risk of nicotine abuse or dependence in early adulthood than lower trajectories.

Evidence on hyperactivity symptom score trajectories and similar smoking outcomes is inconclusive. Literature on symptom trajectories in low socioeconomic boys is sorely lacking; no study has evaluated the association of symptom score trajectories with smoking outcomes. Second, in a sample of 1,037 boys from low socioeconomic neighborhoods, I derived trajectories of hyperactivity and inattention symptom scores between childhood and mid-adolescence (ages 6-15 years), using teachers’ and mothers’ ratings, separately. I also evaluated risk factors for high symptom score trajectories. Three trajectories were identified for both hyperactivity and inattention symptom scores. Hyperactivity symptom scores generally declined over time (high declining, moderate declining, and low declining), whereas inattention symptom scores remained stable (high stable, moderate stable, and low stable). Most boys had low symptom scores over time (i.e., low declining for hyperactivity or low stable for inattention), but approximately one-fifth to one-third followed high symptom score trajectories (high declining for hyperactivity or high stable for inattention).

Mothers were more likely than teachers to rate boys as having higher symptom scores. Boys’ behavioral symptom scores (hyperactivity, inattention, opposition, and anxiety) at age 6 years and lack of family intactness were risk factors for high hyperactivity and inattention symptom score trajectories. Third, in the same sample of boys from low socioeconomic neighborhoods, I assessed the associations of the hyperactivity and inattention symptom score trajectories with frequency of cigarette smoking at ages 16-17 years (late adolescence) and daily and heavy (≥1 pack/day) smoking at ages 23 and 28 years (young adulthood). I further conducted mediational analyses to assess the potential impact of cigarette smoking frequency and use of alcohol, marijuana, and other drugs in late adolescence on smoking outcomes in young adulthood. High vs. low symptom score trajectories of hyperactivity (i.e., high declining vs. low declining) and inattention (i.e., high stable vs. low stable) were associated with nearly doubled odds of high cigarette smoking frequency (≥40 times in the past year) in late adolescence (hyperactivity: OR=1.97 [95% CI=1.30-2.98]; inattention: OR=1.87 [1.27-2.76]).

High (vs. low) symptom score trajectory of inattention, but not hyperactivity, was further associated with elevated risk for daily cigarette smoking (OR=2.67 [1.53-4.64]) and heavy cigarette smoking (OR=1.95 [1.10-3.45]) in young adulthood. Part of the associations (about 11-23%) was mediated by high cigarette smoking frequency in late adolescence. The mediation roles of other substances were not statistically significant. Although the socioeconomically disadvantaged boys whose data I analyzed were similar in number of symptom score trajectories and trends (declining for hyperactivity and stable for inattention) to boys in general populations, they were at elevated risk for high scores for both of the symptom domains over time. Childhood behavioral problems as well as lack of family intactness were associated with high symptom score trajectories of both hyperactivity and inattention. High trajectories of both hyperactivity and inattention scores were associated with high risk of cigarette smoking frequency in late adolescence, but inattention appeared to have a longer-term impact on smoking behaviors.

Altogether, my research findings suggest that children with high symptom levels of hyperactivity and/or inattention at an early age, especially those with symptoms that persist over time, might benefit from early interventions to manage and reduce their symptoms and their risk of becoming cigarette smokers.