SAN DIEGO (FRONTLINE MEDICAL NEWS) – Among adolescent daily cigarette smokers, the individual and concomitant use of alcohol, marijuana, and tobacco have unique and common associations with reinforcement sensitivity, with negative affect, and with electrophysiological signatures of reward function, results from a novel study demonstrated.

“The co-use of alcohol, marijuana, and tobacco in youth are associated bidirectionally with higher rates of substance use, higher levels of addiction severity, and with poorer treatment outcomes for youth who present for treatment,” lead study author Christopher J. Hammond, MD , said at the annual meeting and scientific symposium of the American Academy of Addiction Psychiatry.

“Recent national population studies suggest that rates of co-use of these drugs are increasing, so it’s important to have a better understanding of why certain individuals use these drugs together, and what the interactive effects of these drugs are,” Dr. Hammond explained.

Currently, the effects of combined alcohol, marijuana, and tobacco use on brain function are poorly understood, noted Dr. Hammond of the division of child and adolescent psychiatry at Johns Hopkins Bayview Medical Center, Baltimore.

Published studies to date suggest that alcohol, marijuana, and tobacco use disorders are linked separately to dysfunction in the neural substrates of reward and punishment processing, but none has examined co-use or comorbid disorders in adolescents.

In a cross-sectional, single-visit study, Dr. Hammond and his associates examined a population of 36 adolescent non-deprived daily cigarette smokers and 29 healthy controls from the greater New Haven, Conn., area, matched for age, gender, and grade level. The subjects ranged in age from 14 to 20 years and were administered self-report measures characterizing tobacco, marijuana, and alcohol use. The researchers also collected urine and breathalyzer measures to characterize tobacco and cannabis use.

All subjects completed a number of self-report questionnaires characterizing their substance use patterns, their addiction severity, impulsivity, sensitivity to reward and punishment, and depression. They also underwent a 45-minute EEG, during which they completed a resting EEG test and completed a reward task.

The adolescent daily cigarette smoker group had blunted or decreased sensitivity to punishment and increased impulsivity, compared with the healthy controls, Dr. Hammond reported.

Co-occurring drug use was high in the adolescent daily smoker group, with 80% reporting heavy marijuana use (defined as using it over 100 times during adolescence), and 67% reporting heavy episodic binge drinking (defined as consuming greater than four alcoholic beverages for females during one sitting and greater than five for males at least two or more times a month).

One out of two of the daily cigarette smokers were also daily marijuana smokers, and about 75% of the adolescent smokers had a positive urine drug screen for marijuana. They smoked an average of eight cigarettes per day, used cannabis about 17 days out of the month, and they had about 1.5 binge drinking episodes per month.

Next, the researchers used linear regression analyses to examine which of the psychological variables were associated with alcohol, marijuana, and tobacco use severity within the smoker group, after co-varying for age, gender, race/ethnicity, and full-scale IQ.

“For alcohol use, we found that depression, sensitivity to reward, and impulsivity were significantly associated with alcohol problem severity scores, even after controlling for sociodemographics and other drug use (P less than .05),” Dr. Hammond said.

“For marijuana use, we found that sensitivity to reward and impulsivity were significantly associated with cannabis problem severity, even after controlling for demographics and alcohol and other drug use (P less than .01),” he continued. “For tobacco use, we found that anxiety sensitivity was significantly associated with nicotine dependence scores, even after controlling for demographics and alcohol and marijuana use (P less than .001).”

On EEG analyses, the researchers found no main effects for group or group by condition for the feedback-related negativity (FRN) signal or for the event-related Theta oscillation between the adolescent non-deprived smokers and the healthy controls.

However, examination of the smoker subgroups revealed a unique and shared association between alcohol, marijuana, and tobacco and the EEG signals.

“With regard to substance use associations with the FRN smokers, regression analyses showed that cannabis use problem severity was associated with an increased FRN amplitude during the reward condition only,” Dr. Hammond said. “This finding remained significant after co-varying for demographics, for other drug use, for nicotine dependence and alcohol severity as well.

“We also found an association between alcohol problem severity and mean FRN amplitude, but with no differences across conditions,” he added. There was an association also “ between nicotine dependence and decreased FRN latency, but only during the reward and draw conditions, suggesting a nicotine severity association with speed of processing salient reward and stimuli.”

While the findings need to be better studied and replicated, “these associations may be leveraged to better personalize our interventions for these different substances of abuse,” Dr. Hammond observed. “The study also provides preliminary evidence for a dual-process model of substance use, specifically for cannabis. Cannabis severity in adolescent smokers is associated with increased bottom-up reward signaling and impaired top-down cognitive control over a salient or rewarding stimulus.”

The study was supported by the American Academy of Child and Adolescent Psychiatry and the National Institute on Drug Abuse. Dr. Hammond disclosed that he receives research funding from both organizations.

SOURCE: Hammond et al. AAAP 2017. Paper session A3.


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