Substance use patterns in 9-10 year olds: Baseline findings from the adolescent brain cognitive development (ABCD) study

BACKGROUND

The Adolescent Brain Cognitive Development ™ Study (ABCD Study®) is an open-science, multi-site, prospective, longitudinal study following over 11,800 9- and 10-year-old youth into early adulthood. The ABCD Study aims to prospectively examine the impact of substance use (SU) on neurocognitive and health outcomes. Although SU initiation typically occurs during teen years, relatively little is known about patterns of SU in children younger than 12.

METHODS

This study aims to report the detailed ABCD Study® SU patterns at baseline (n = 11,875) in order to inform the greater scientific community about cohort's early SU. Along with a detailed description of SU, we ran mixed effects regression models to examine the association between early caffeine and alcohol sipping with demographic factors, externalizing symptoms and parental history of alcohol and substance use disorders (AUD/SUD).

PRIMARY RESULTS

At baseline, the majority of youth had used caffeine (67.6 %) and 22.5 % reported sipping alcohol (22.5 %). There was little to no reported use of other drug categories (0.2 % full alcohol drink, 0.7 % used nicotine, <0.1 % used any other drug of abuse). Analyses revealed that total caffeine use and early alcohol sipping were associated with demographic variables (p's<.05), externalizing symptoms (caffeine p = 0002; sipping p = .0003), and parental history of AUD (sipping p = .03).

CONCLUSIONS

ABCD Study participants aged 9-10 years old reported caffeine use and alcohol sipping experimentation, but very rare other SU. Variables linked with early childhood alcohol sipping and caffeine use should be examined as contributing factors in future longitudinal analyses examining escalating trajectories of SU in the ABCD Study cohort.

Mental disorders as risk factors for later substance dependence: estimates of optimal prevention and treatment benefits

BACKGROUND

Although mental disorders have been shown to predict subsequent substance disorders, it is not known whether substance disorders could be cost-effectively prevented by large-scale interventions aimed at prior mental disorders. Although experimental intervention is the only way to resolve this uncertainty, a logically prior question is whether the associations of mental disorders with subsequent substance disorders are strong enough to justify mounting such an intervention. We investigated this question in this study using simulations to estimate the number of substance disorders that might be prevented under several hypothetical intervention scenarios focused on mental disorders.

METHOD

Data came from the National Comorbidity Survey Replication (NCS-R), a nationally representative US household survey that retrospectively assessed lifetime history and age of onset of DSM-IV mental and substance disorders. Survival analysis using retrospective age-of-onset reports was used to estimate associations of mental disorders with subsequent substance dependence. Simulations based on the models estimated effect sizes in several hypothetical intervention scenarios.

RESULTS

Although successful intervention aimed at mental disorders might prevent some proportion of substance dependence, the number of cases of mental disorder that would have to be treated to prevent a single case of substance dependence is estimated to be so high that this would not be a cost-effective way to prevent substance dependence (in the range 76-177 for anxiety-mood disorders and 40-47 for externalizing disorders).

CONCLUSIONS

Treatment of prior mental disorders would not be a cost-effective way to prevent substance dependence. However, prevention of substance dependence might be considered an important secondary outcome of interventions for early-onset mental disorders.

Drug abuse and developmental psychopathology

Drug abuse research and theory has become much more sophisticated over the last 2 decades, and some of the advancements parallel concepts that are part of the developmental psychopathology approach. The application of the developmental psychopathology perspective to recent drug abuse research findings can provide a greater understanding of that information and point to important areas of future research. Among the drug abuse research areas discussed here and viewed from this perspective are antecedent and co-occurring psychopathological conditions and other problem behaviors; the diversity of the nature of, paths to, and processes and outcomes related to drug abuse; the role of intermediary influences; the interaction of individual and environmental predisposing and protective factors; the role of families and other social institutions in intervention; and developmental stage characteristics. Directions for future research are also discussed.

A twin study on sensation seeking, risk taking behavior and marijuana use

The contribution of genetic and environmental factors to the covariation between risk-taking and marijuana use was assessed in adolescent twins. Genetic factors were found to significantly influence some traits (i.e. risk-taking attitude), while familial environmental factors were important for others (i.e. sexual promiscuity). For marijuana use, genetic and environmental factors were equally important; however, the association between risk taking and marijuana use may not be comparable for different behaviors. Results suggest that different etiological factors may underlie various risk taking traits which is relevant to both prevention efforts and attempts to identify genes involved in risk taking and shared genetic influences with substance use.

Child psychopathology risk factors for drug abuse: overview

Introduces the special section on Child Psychopathology Risk Factors for Substance Use Disorders. This article summarizes important principles, the current literature, contributions to this section, and issues for future research. Psychopathological conditions are strongly associated with substance use disorders, and some childhood psychopathological conditions may constitute precursors to this comorbidity. Conduct disorder constitutes a strong risk factor for substance use disorders, and bipolar disorder, although more rare, may also constitute a significant risk. Data for other child psychiatric conditions are mixed or lacking; however, important subgroups may be at risk and merit further attention. Underlying characteristics, such as temperament and self-regulation, merit further study as possible explanatory variables. Such studies hold the key for targeting and improving preventive and therapeutic interventions.

Adolescent substance abuse: a review of the past 10 years

OBJECTIVE

To review and synthesize the recent scientific literature on adolescent substance abuse, covering natural history, epidemiology, etiology, comorbidity, assessment, treatment, and prevention, and to highlight areas for future research.

METHOD

Studies of adolescent substance abuse were reviewed with the focus on substance abuse and dependence rather than substance use.

RESULTS

There has been a sharp recent resurgence in adolescent drug use. Biological factors, including genetic and temperament characteristics, as well as family environment factors, are emerging as important etiological variables. Comorbidity with other psychiatric disorders, particularly with conduct disorder, is frequent and complicates treatment. New assessment instruments are available for clinical and research use. Among treatment modalities, family-based interventions have received the most study.

CONCLUSIONS

The past decade has seen growth in the volume and sophistication of research on adolescent substance abuse and in the conceptualization of this problem. Further research is needed, particularly on the significance of comorbid conditions and on individualized and effective treatment approaches.

Effects of different exercise training intensities on lipoprotein cholesterol fractions in healthy middle-aged men

Exercise training has been associated with decreases in total cholesterol and increases in high-density lipoprotein (HDL) cholesterol. The effect of the intensity of the exercise on alterations in cholesterol and lipoprotein fractions has not been defined and is the subject of this study. We divided 49 healthy men (aged 44 +/- 8 years) into four groups and evaluated them before and after 12 weeks of cycle ergometer exercise training at (1) an intensity of 65% of maximal achieved heart rate, (2) 75% maximal heart rate, (3) 85% maximal heart rate, and (4) a 12-week nonexercise control period. Pre- and post-training evaluations included maximal ergometer exercise ECG examinations with measurement of maximal minute oxygen consumption and serum total cholesterol, HDL cholesterol, and triglyceride levels. Low-density (LDL) and very low-density lipoprotein (VLDL) cholesterol levels were calculated. Dietary histories were obtained before and after the training period, and body weight and percentage of body fat were measured. Post-training oxygen uptake was significantly increased (training effect) in the groups exercising to 65%, 75%, and 85% maximal heart rate. Results of within-group analysis showed significant increases in the HDL cholesterol fractions in the 75% and 85% groups but not in the 65% group or the control group. Significant decreases in calculated LDL fractions occurred only in the 75% exercise-trained group with maximal heart rate. Aerobic exercise training favorably alters plasma lipoprotein profiles. A minimum training intensity equal to 75% maximal heart rate is required to the increase HDL cholesterol level.

Isolation and characterization of human liver guanine deaminase

Guanine deaminase (EC 3.5.4.3, guanine aminohydrolase [GAH]) was purified 3248-fold from human liver to homogeneity with a specific activity of 21.5. A combination of ammonium sulfate fractionation, and DEAE-cellulose, hydroxylapatite, and affinity chromatography with guanine triphosphate ligand were used to purify the enzyme. The enzyme was a dimer protein of a molecular weight of 120,000 with each subunit of 59,000 as determined by gel filtration and sodium dodecyl sulfate-gel electrophoresis. Isoelectric focusing gave a pI of 4.76. It was found to be an acidic protein, as evidenced by the amino acid analysis, enriched with glutamate, aspartate, alanine and glycine. It showed a sharp pH optimum of 8.0. The apparent Km for guanine was determined to be 1.53 X 10(-5) M at pH 6.0 and 2 X 10(-4) M for 8-azaguanine as a substrate at pH 6.0. The enzyme was found to be sensitive to p-hydroxymercuribenzoate inhibition with a Ki of 1.53 X 10(-5) M and a Ki of 5 X 10(-5) M with 5-aminoimidazole-4-carboxamide as an inhibitor. The inhibition with iodoacetic acid showed only a 7% loss in the activity at 1 X 10(-4) M and a 24% loss at 1 X 10(-3) M after 30 min of incubation, whereas p-hydroxymercuribenzoate incubation for 30 min resulted in a 91% loss of activity at a concentration of 1 X 10(-4) M. Guanine was the substrate for all of the inhibition studies. The enzyme was observed to be stable up to 40 degrees C, with a loss of almost all activity at 65 degrees C with 30 min incubation. Two pKa values were obtained at 5.85 and 8.0. Analysis of the N-terminal amino acid proved to be valine while the C-terminal residue was identified as alanine.

ESR analysis of the FAD in bovine liver monoamine oxidase

Two hydrazine spin labels, 1-oxyl-2,2,5,5-tetramethylpyrroline-3-carbonyl ethyl hydrazine and 1-oxyl-2,2,6,6-tetramethylpiperidino-4-hydrazine, were synthesized as probes of the FAD binding site of monoamine oxidase. The reporter nitroxide moiety showed an ESR spectrum classified as partially immobilized which is indicative of FAD near the surface of the enzyme. Attempts to pick up flavin semiquinone or free radical intermediates during substrate oxidation with the spin traps 5,5-dimethyl-1-pyrroline-1-oxidase and phenyl-t-butylnitrone were not successful.

Topographical distribution of purine nucleoside phosphorylase in the human neuraxis

The activity of purine nucleoside phosphorylase was determined at various levels of the human neuraxis in 5 brains and 2 spinal cords, using the method of Lewis and Glantz. The determination is based on the decrease in optical density of guanosine at 252 nm and 40 degrees C, with conversion of this compound to guanine and ribose-1-phosphate by phosphorolysis. Our studies show a fairly uniform distribution of the enzyme in the human CNS, with an average value of 209 mumol of guanosine transformed/min/g of wet tissue. The lowest values are found in the spinal cord and cerebellar grey matter, and highest amounts in the occipital grey and white substance.

Bovine brain purine-nucleoside phosphorylase purification, characterization, and catalytic mechanism

Bovine brain purine-nucleoside phosphorylase (purine-nucleoside:orthophosphate ribosyltransferase, EC 2.4.2.1) was purified to homogeneity at a specific activity of 78 mumol min-1 mg of protein-1. A molecular weight of 78 000-80 000 was calculated for the native enzyme by fel filtration on Sephadex. Gel electrophoresis in the presence of sodium dodecyl sulfate indicated subunits of molecular weight of 38 000. Chemical and kinetic studies strongly implicated histidine and cysteine as catalytic groups at the active site of the enzyme. The pKa's determined for ionizable groups at the active site of the free enzyme were 5.8 and 8.2. Enzyme completely inactivated by p-chloromercuribenzoate was partially reactivated enzyme. A strong susceptibility to photooxidation in presence of methylene blue was observed. Photoinactivation was pH dependent, implicating histidine as the susceptible group at the active site. A rapid loss of catalytic activity upon incubation at 55 degrees C suggested heat lability. An activation energy of 9.6 kcal/mol was calculated. The nature of the catalytic mechanism of the enzyme was investigated, and initial velocity studies showed linear converging patterns of double-reciprocal plots of the data, consistent with a sequential catalytic mechanism. The product inhibition pattern was at variance with both the ordered Bi-Bi and random mechanisms. The observed competition between purine and nucleoside, and between inorganic orthophosphate and ribose 1-phosphate for this ordered mechanism, suggest a Theorell-Chance mechanism. Michaelis constants determined for substrates of the enzyme were 4.35 X 10(-5) M for guanosine, 3.00 X 10(-5) M for guanine, and 2.15 X 10(-2) M for inorganic orthophosphate.

Monomeric purine nucleoside phosphorylase from rabbit liver. Purification and characterization

Rabbit liver purine nucleoside phosphorylase (purine nucleoside: orthophosphate ribosyltransferase EC 2.4.2.1.) was purified to homogeneity by column chromatography and ammonium sulfate fractionation. Homogeneity was established by disc gel electrophoresis in presence and absence of sodium dodecyl sulfate, and isoelectric focusing. Molecular weights of 46,000 and 39,000 were determined, respectively, by gel filtration and by sodium dodecyl sulfate-polyacrylamide disc gel electrophoresis. Product inhibition was observed with guanine and hypoxanthine as strong competitive inhibitors for the enzymatic phosphorolysis of guanosine. Respective Kis calculated were 1.25 x 10(-5) M for guanine and 2.5 x 10(-5) M for hypoxanthine. Ribose 1-phosphate, another product of the reaction, gave noncompetitive inhibition with guanosine as variable substrate, and an inhibition constant of 3.61 x 10(-4) M was calculated. The protection of essential --SH groups on the enzyme, by 2-mercaptoethanol or dithiothreitol, was necessary for the maintenance of enzyme activity. Noncompetitive inhibition was observed for p-chloromercuribenzoate with an inhibition constant of 5.68 x 10(-6)M. Complete reversal of this inhibition by an excess of 2-mercaptoethanol or dithiothreitol was demonstrated. In the presence of methylene blue, the enzyme showed a high sensitivity to photooxidation and a dependence of photoinactivation on pH, strongly implicating histidine as the susceptible group at the active site of the enzyme. The pKa values determined for ionizable groups of the active site of the enzyme were near pH 5.5 and pH 8.5 The chemical and kinetic evidences suggest that histidine and cysteine may be essential for catalysis. Inorganic orthophosphate (Km 1.54 x 10(-2) M) was an obligatory anion requirement, and arsenate substituted for phosphate with comparable results. Guanosine (Km 5.00 x 10(-5) M), deoxyguanosine (Km 1.00 x 10(-4)M) and inosine (Km 1.33 x 10(-4)M), were substrates for enzymatic phosphorolysis. Xanthosine was an extremely poor substrate, and adenosine was not phosphorylyzed at 20-fold excess of the homogeneous enzyme. Guanine (Km 1.82 x 10(-5)M),ribose 1-phosphate (Km 1.34 x 10(-4) M) and hypoxanthine were substrates for the reverse reaction, namely, the enzymatic synthesis of nucleosides. The initial velocity studies of the saturation of the enzyme with guanosine, at various fixed concentrations of inorganic orthophosphate, suggest a sequential bireactant catalytic mechanism for the enzyme.