3.1 Prevalence of past-year substance use and mental health problems
summarizes the past-year prevalence estimates of substance use, internalizing and externalizing problems by age groups. Overall, rates of substance dependence outnumbered abuse in all age groups, but went up with age. The prevalence of a specific substance use problem varied by age groups: alcohol, cocaine and opioid use were more prevalent in adults than in adolescents, while cannabis, alcohol, poly-substance, and other drug use not otherwise specified (NOS) were more common in adolescents and young adults.
Prevalence (%) of Past-year Substance Use Problems and Co-occurring Mental Health Problems by Age Groupsa
With regard to substance use patterns, the most prevalent substance-specific use problem among adolescents under age 15 was cannabis (41.6%), followed by alcohol (21.7%), poly-substance dependence (16.1%) and other drug use-NOS (12.8%). A similar substance use pattern was also observed for adolescents ages 15 to 17. For young adults (age 18-25), the most prevalent substance use problems were cannabis (40.8%) and alcohol (38.9%), followed by cocaine (22.8%), other drug use-NOS (10.6%), opioid (9.6%) and poly-substance dependence (7.5%). For adults ages 26-39, the prevalence of a cocaine use problem (62.9%) far outnumbered the prevalence of other substance use problems, followed by alcohol (37.3%), opioid (19.9%), cannabis (13.3%) and other drug use-NOS (6.5%). For adults at age 40 or more, the most prevalent substance use problem was cocaine use (58.5%), followed by alcohol (44%), and opioid (21.8%). For both adolescent and adult clients, amphetamine, hallucinogens, inhalants, and sedative use problems were less prevalent. For example, rates of an amphetamine use problem were 2.2% in young adolescents under age 15, 3.9% in adolescents ages 15-17, 7.6% in young adults ages 18-25, 3.6% in adults ages 26-39 and 0.6% in adults over age 40. Among all specific substance use problems, PCP use was the least prevalent problem observed.
Overall, two thirds of clients presenting to substance abuse treatment in each age group had at least one mental health problem. The rates of internalizing problems generally increased with age. About one third of adolescents and half of adults endorsed depressive symptoms in the year prior to entering substance abuse treatment. Anxiety was prevalent among adults over age 25. In contrast, the rates of externalizing problems generally decreased with age: going from two thirds of adolescent groups to one third of the oldest group. Approximately half of adolescents under 15 had ADHD and about one third of adults met criteria for ADHD. It was estimated that half of adolescents and one third of adults met criteria for CD. The co-occurrence of manifesting both internalizing and externalizing behaviors was high among our dependent clients. More than 40% of adolescents and young adults endorsed symptoms for both internalizing and externalizing problems, and about 38% of adults ages 26-39 and 35% of adults ages 40 or more had both internalizing and externalizing problems in the year prior to entering treatment.
3.2 Comorbidity of past-year substance dependence with mental health problems
presents the prevalence of past-year internalizing and externalizing problems by past-year substance dependence status, and the association between past-year substance dependence and each past-year internalizing and externalizing problem expressed as an odds ratio (OR). These ORs represent the likelihood of having the specified co-occurring mental health problem for those with past-year substance dependence compared to those without substance dependence. Values greater than 1 suggest increased likelihood and less than 1.00 suggest reduced likelihood. Across all age groups, rates of co-occurring mental health problem were higher among clients with past-year substance dependence than those without. All of the co-occurring problems were positively associated with substance dependence across ages such that having dependence as associated with higher rates of having each co-occurring problem (ORs=2.9-8.8). The trends and strength of association, however, varied by age.
Prevalence and Odds Ratio of the Association of Past-year Dependent Status Relative to the Non-dependent Status with Past-Year Co-occurring Problemsa
Among dependent adolescents under age 15, about 90% had at least one mental health problem in the past year. More specifically, 69.2 % were identified as having at least one internalizing problem and 81.3% for at least one externalizing problem. Dependent youth were at a five-fold elevated likelihood of having an internalizing problem compared to those who were not past-year dependent (OR=5.0, 95% confident interval (CI) =3.7-6.8). CD (74.2%), ADHD (63.6%), depression (52.7%) and traumatic distress (50.6%) were the most prevalent co-occurring problems among those dependent youth under age 15. The estimated odds ratios of comorbidity were 3.4 (95% CI=2.4-4.5) for CD, 3.0 (95% CI=2.2-3.9) for ADHD, 5.6 (95% CI=4.1-7.8) for depression and 2.9 (95% CI=2.2-3.9) for traumatic distress. The rate of anxiety among young dependents was 24.6% and the estimated odds ratio of dependents relative to non-dependents with anxiety was 4.6 (95% CI=3.0-7.2). It is estimated that about 61% of young dependents had both internalizing and externalizing problems. A similar comorbidity pattern was observed for adolescents age 15-17, in which the externalizing problems were the most prevalent co-occurring problems; yet, the estimated risks were greater for having both internalizing and externalizing behaviors than each problem alone.
Unlike high co-occurrence of externalizing problems discovered among adolescents, dependent adults endorsed more symptoms of internalizing problems. Using young adults between ages 18 and 25 as an example, 76.7% and 66.6% were identified as having at least one internalizing problem and at least one externalizing problem, respectively. The strength of association between substance dependence and co-occurring problems remained strong; dependent clients were 6 times more likely to have an internalizing problem (95% CI=4.2-8.5) and 8.4 times more likely to have an externalizing problem (95% CI=5.7-12.2) than non-dependent clients. Traumatic distress (63.7%), depression (55.5%), CD (55.5%) and ADHD (54.7) were the most prevalent co-occurring problems among dependent clients between ages 18 and 25. The estimated odds ratios for those with dependence relative to those without were 4.0 (95% CI= 2.8-5.6) for traumatic stress, 4.6 (95% CI=3.2-6.7) for depression, 8.2 (95% CI=5.4-12.4) for CD and 7.9 (95% CI=5.2.-12.0) for ADHD. These young dependent adults were found to be at the most elevated risk for having both internalizing and externalizing problems compared to those in other age groups (OR=8.8, 95% CI=5.8-13.2). Among adults age 40 or older, the strongest association between substance dependence and co-occurring problems was ADHD (OR=7.3, 95% CI=3.5-15.1), followed by anxiety (OR=6.5, 95% CI=3.9-10.8) and CD (OR=5.2, 95% CI=2.4-11.1), although with wider confidence intervals. Overall, the findings with respect to comorbidity between substance dependence and co-occurring problems indicated that, for adolescents, the magnitude of comorbidity with substance dependence was greater for internalizing problems, while it was greater for externalizing problems for adults. Both young adults and older adults were at relatively elevated risk for having both internalizing and externalizing problems prior to treatment entry.