Anthony Liguori

Impulsivity, attention, memory, and decision-making among adolescent marijuana users

RationaleMarijuana is a popular drug of abuse among adolescents, and they may be uniquely vulnerable to resulting cognitive and behavioral impairments. Previous studies have found impairments among adolescent marijuana users. However, the majority of this research has examined measures individually rather than multiple domains in a single cohesive analysis. This study used a logistic regression model that combines performance on a range of tasks to identify which measures were most altered among adolescent marijuana users.ObjectivesThe purpose of this research was to determine unique associations between adolescent marijuana use and performances on multiple cognitive and behavioral domains (attention, memory, decision-making, and impulsivity) in 14- to 17-year-olds while simultaneously controlling for performances across the measures to determine which measures most strongly distinguish marijuana users from nonusers.MethodsMarijuana-using adolescents (n = 45) and controls (n = 48) were tested. Logistic regression analyses were conducted to test for: (1) differences between marijuana users and nonusers on each measure, (2) associations between marijuana use and each measure after controlling for the other measures, and (3) the degree to which (1) and (2) together elucidated differences among marijuana users and nonusers.ResultsOf all the cognitive and behavioral domains tested, impaired short-term recall memory and consequence sensitivity impulsivity were associated with marijuana use after controlling for performances across all measures.ConclusionsThis study extends previous findings by identifying cognitive and behavioral impairments most strongly associated with adolescent marijuana users. These specific deficits are potential targets of intervention for this at-risk population.

Tanning as an addictive behavior: a literature review

Background: Recent studies have identified reinforcing properties associated with tanning and suggest a possible physiologic mechanism and addiction driving tanning behavior.

Cognitive, psychomotor and polysomnographic effects of trazodone in primary insomniacs.

Trazodone is prescribed widely as a sleep aid, although it is indicated for depression, not insomnia. Its daytime cognitive and psychomotor effects have not been investigated systematically in insomniacs. The primary goal of this study was to quantify, in primary insomniacs, the hypnotic efficacy of trazodone and subsequent daytime impairments. Sixteen primary insomniacs (mean age 44 years) participated, with insomnia confirmed by overnight polysomnography (sleep efficiency ≤ 85%). Trazodone 50 mg was administered to participants 30 min before bedtime for 7 days in a 3‐week, within‐subjects, randomized, double‐blind, placebo‐controlled design. Subjective effects, equilibrium (anterior/posterior body sway), short‐term memory, verbal learning, simulated driving and muscle endurance were assessed the morning after days 1 and 7 of drug administration. Sleep was evaluated with overnight polysomnography and modified Multiple Sleep Latency Tests (MSLT) on days 1 and 7. Trazodone produced small but significant impairments of short‐term memory, verbal learning, equilibrium and arm muscle endurance across time‐points. Relative to placebo across test days, trazodone was associated with fewer night‐time awakenings, minutes of Stage 1 sleep and self‐reports of difficulty sleeping. On day 7 only, slow wave sleep was greater and objective measures of daytime sleepiness lower with trazodone than with placebo. Although trazodone is efficacious for sleep maintenance difficulties, its associated cognitive and motor impairments may provide a modest caveat to health‐care providers.

Involvement of cholinergic neuronal systems in intravenous cocaine self-administration.

Recent studies suggest the participation of cholinergic neurons in the brain processes underlying reinforcement. The involvement of cholinergic neurons in cocaine self-administration has been recently demonstrated in studies using muscarinic and nicotinic agonists and antagonists, microdialysis, assessment of choline acetyltransferase activity and acetylcholine (ACh) turnover rates. The present experiment was initiated to identify subsets of cholinergic neurons involved in the brain processes that underlie cocaine self-administration by lesioning discrete populations with a selective neurotoxin. Rats were trained to self-administer cocaine and the cholinergic neurotoxin 192-IgG-saporin or vehicle was then bilaterally administered into the posterior nucleus accumbens (NAcc)-ventral pallidum (VP). The 192-IgG-saporin induced lesions resulted in a pattern of drug-intake consistent with either a shift in the dose intake relationship to the left or downward compared to sham-treated controls. A second experiment used a self-administration threshold procedure that demonstrated this lesion shifted the dose intake relationship to the left compared to the sham-vehicle treated rats. The magnitude and extent of the lesion was assessed by measuring the expression of p75 (the target for 192-IgG-saporin) and choline acetyltransferase (ChAT) in the NAcc, VP, caudate nucleus-putamen (CP) and vertical limb of the medial septal nucleus-diagonal band (MS-DB) of these rats using real time reverse transcriptase-polymerase chain reaction. Significant reductions in gene expression for p75 (a selective marker for basal forebrain cholinergic neurons) and ChAT were seen in the MS-DB and VP while only small decreases were seen in the NAcc and CP of the 192-IgG-saporin treated rats. These data indicate that the overall influence of cholinergic neurons in the MS-DB and VP are inhibitory to the processes underlying cocaine self-administration and suggest that agonists directed toward subclasses of cholinergic receptors may have efficacy as pharmacotherapeutic adjuncts for the treatment of cocaine abuse.

Failure to sustain prepulse inhibition in adolescent marijuana users

BACKGROUND Marijuana use is typically initiated during adolescence, which is a critical period for neural development. Studies have reported reductions in prepulse inhibition (PPI) among adults who use marijuana chronically, although no human studies have been conducted during the critical adolescent period. METHODS This study tested PPI of acoustic startle among adolescents who were either frequent marijuana users or naïve to the drug (Controls). Adolescents were tested using two intensities of prepulses (70 and 85 dB) combined with a 105 dB startle stimulus, delivered across two testing blocks. RESULTS There was a significant interaction of group by block for PPI; marijuana users experienced a greater decline in the PPI across the testing session than Controls. The change in PPI of response magnitude for users was predicted by change in urine THC/creatinine after at least 18 h of abstinence, the number of joints used during the previous week before testing, as well as self-reported DSM-IV symptoms of marijuana tolerance, and time spent using marijuana rather than participating in other activities. CONCLUSIONS These outcomes suggest that adolescents who are frequent marijuana users have problems maintaining prepulse inhibition, possibly due to lower quality of information processing or sustained attention, both of may contribute to continued marijuana use as well as attrition from marijuana treatment.

Self-estimation of blood alcohol concentration: A review

This article reviews the history of blood alcohol concentration (BAC) estimation training, which trains drinkers to discriminate distinct BAC levels and thus avoid excessive alcohol consumption. BAC estimation training typically combines education concerning alcohol metabolism with attention to subjective internal cues associated with specific concentrations. Estimation training was originally conceived as a component of controlled drinking programs. However, dependent drinkers were unsuccessful in BAC estimation, likely due to extreme tolerance. In contrast, moderate drinkers successfully acquired this ability. A subsequent line of research translated laboratory estimation studies to naturalistic settings by studying large samples of drinkers in their preferred drinking environments. Thus far, naturalistic studies have provided mixed results regarding the most effective form of BAC feedback. BAC estimation training is important because it imparts an ability to perceive individualized impairment that may be present below the legal limit for driving. Consequently, the training can be a useful component for moderate drinkers in drunk driving prevention programs.

Caffeine self-administration in humans: 1. Efficacy of cola vehicle.

Eight exclusive cola drinkers in Experiment 1 (mean caffeine intake = 157 +/- 74 mg/day) and 16 drinkers of both cola and coffee in Experiment 2 (mean caffeine intake = 579 +/- 201 mg/day) underwent 6 independent, double-blind weekly trials. Each trial began with a randomized cross-over sampling period of 1 day of access to noncaffeinated cola and 1 day of access to caffeinated (33 mg/8 oz) cola. During the subsequent 1- or 2-day test period, participants had unlimited concurrent access to the 2 colas. Reliable caffeine self-administration occurred in 2 of 8 participants in Experiment 1 and in 4 of 16 participants in Experiment 2. Self-reported drowsiness, fatigue, and headache were higher when participants received only placebo colas in Experiment 2, but not Experiment 1. Caffeine self-administration via cola occurs both among people whose primary source of caffeine is cola and among those whose primary source of caffeine is coffee.

Indoor tanning relieves pain.

To the Editor, Despite deleterious effects of ultraviolet (UV) radiation, tanning remains popular, particularly among young women (1). Between 1986 and 1996, tanning bed usage in the United States rose by 300% (1). While the physical appearance of tanned skin is thought to be the primary motivator, physiologic effects of UV are also important (2). In a controlled, blinded, repeated-choice trial using visually indistinguishable tanning beds, one with an acrylic filter that transmits UV light, the other with an identical appearing filter that blocks UV light, 11 of 14 frequent tanners consistently preferred the UV emitting bed (2). One subject – a 27-year-old woman who suffered from chronic lower back pain – reported alleviation of her back pain and an overall sensation of relaxation with tanning. She reported pain relief that lasted for 5–6 h during or shortly after tanning. The UV bed improved her pain to a greater degree than the non-UV bed. Many frequent tanners perceive the sense of relaxation derived from UV as a primary benefit of tanning (2, 3). Alternative therapies are commonly used to relieve chronic low back pain, and some patients may tan because of its effect on pain (4). The alleviation of back pain by tanning illustrates that physiologic factors may play a role in driving tanning behavior. While the efficacy of UV radiation in the relief of chronic pain is unknown, further investigation is needed. Acknowledgements Funding: The Center for Dermatology Research is funded by a grant from Galderma Laboratories, L.P.

Alcohol Effects on Simulated Driving in Frequent and Infrequent Binge Drinkers

Compared with non‐bingers, binge drinkers are more likely to drive while intoxicated. The extent to which binge frequency impacts confidence in driving and subsequent driving impairment is unknown. This study compared the effects of an experimenter‐delivered alcohol binge on subjective impairment and simulated driving ability in female high‐frequency and low‐frequency bingers.

Cognitive impairments in adolescent cannabis users are related to THC levels

ObjectivesStudies of the neurocognitive impairments resulting from cannabis use have primarily depended on self-reports to classify heavy versus light cannabis use. Several factors such as body mass and individual differences in tetrahydro Cannabinol (THC) metabolism can lead to a large range of circulating levels of THC among persons who report similar cannabis use. This study examined decision-making and attention as a function of urine levels of THC in a sample of adolescents who reported similar frequency of cannabis use. MethodsAdolescents who reported cannabis use at least 4 days per week were assigned to 1 of the 2 groups based on a median split of THC/creatinine ratios on the day of cognitive testing (high THC and low THC). Cognitive testing included a decision-making task and a test of sustained attention. ResultsThe high THC group made significantly more disadvantageous choices on the decision-making task and also performed less accurately on a task of sustained attention compared with the low THC group. ConclusionsThese results suggest that among adolescent cannabis users who are homogenous in their reported frequency of cannabis use, heterogeneity in urine levels of THC is associated with differences in cognitive impairment. Examining the levels of THC metabolites in the urine may uncover differences in cannabis users that may be masked or minimized if users with large variability in their urinary levels of THC are pooled into the same group based on self-reports of cannabis use.