By: Hema Zbogar
Inbred strains of rats differ in how aggressively they seek cocaine after a few weeks of use, according to researchers at the Medical College of Georgia. The finding suggests that genetics plays a role in the relapse of drug-seeking behaviour in humans. The study also found that glutamate, a neurotransmitter involved in learning and memory, plays a role in stirring the cravings that drive some drug users to relapse. Researchers took two strains of inbred rats – Fischer 344 and Lewis – with known genetic differences, enabled each to self-administer cocaine for 14 days, then took the drug away for a week but not the levers the animals used to access it. During the hiatus, the rats received a drug that stimulates glutamate receptors, possible targets for drugs of abuse. It was found that the F344 strain worked harder to get cocaine than the Lewis rats following treatment with the glutamate drug, suggesting they were more susceptible to relapse. The researchers are working to identify the relapse trigger to use as a target for developing ways to curb craving and subsequent relapse. These studies focus on an area of the brain called the nucleus accumbens core, a target for drugs of abuse. Drugs such as cocaine and methamphetamine stimulate release of dopamine in the nucleus accumbens. Dopamine is a neurotransmitter believed to be responsible for the euphoria that comes with drug use. Glutamate, also released in the nucleus accumbens core, may play an equally important role in drug relapse. Drugs such as cocaine appear to alter glutamate neurotransmission in the core, which may contribute to the rewiring of the brain that occurs with drug use.
Psychopharmacology, January 18, 2006 online, doi: 10.1007/s00213-005-0264-4. Paul J. Kruzich and Jinlei Xi, Department of Physiology, Medical College of Georgia, Augusta, Georgia, Department of Pharmacology, School of Medicine, Wuhan University of Science and Technology, Wuhan, Hubei, China.
Personality traits may contribute to suicidal ideation and suicide attempt in young adults, according to researchers at Douglas Hospital in Montreal, Quebec. The researchers investigated the association between personality traits and vulnerability to current suicidal ideation and suicide attempt history in 1,140 adults aged 21–24 years taken from the general population. In all, eight per cent of participants had a history of suicide attempt, and about 60 per cent reported some degree of suicidal ideation. Nine per cent had experienced serious suicidal thoughts. Of 10 personality traits in the analysis, three contributed significantly to suicidal outcomes. Conduct problems were associated with suicide attempts and suicidal ideation, with odds ratios of 1.03 and 1.04, respectively. Identity problems contributed exclusively to suicidal ideation, increasing the risk 1.10-fold. Impulsivity also contributed to suicidal ideation, but was moderated by gender, with impulsive women showing a lower probability of reporting absent-mild suicidal ideation compared with impulsive men. The three personality traits correlated moderately with one another and with psychiatric comorbidity measures. They were also associated with emotional dysregulation. The strongest predictor of concurrent suicidal ideation was history of previous attempt, at an odds ratio of 3.18, but the researchers suggest that for the particular age and cultural group in the study, personality traits may be more useful in predicting current suicidal thoughts than past suicide attempts. The authors call for more research to assess whether these traits are actual risk factors or proxies of a more global risk dimension, which may involve genetic susceptibility or gene-environment interactions.
Psychological Medicine, February 2006, v. 36: 191–202. Jelena Brezo et al., Douglas Hospital Research Centre, Montreal, Quebec.
The tension and turmoil leading up to divorce can be just as damaging to young children as the aftermath, according to research at the University of Alberta. Using data from Statistics Canada’s National Longitudinal Survey of Children and Youth, the study followed about 2,800 children between 1994 and 1998. When the study began, the children were between ages 4–7 and living with both biological parents. In the ensuing four-year period, one parent was interviewed three times about the child’s levels of anxiety, depression and anti-social behaviour. The parent also answered questions about marital satisfaction, depression and family dysfunction. Using the three waves of data, the study compared the mental health of children whose parents remained married with that of the 167 children (6%), whose parents divorced by 1998. The study found that, on average, children from highly dysfunctional families did better after their parents’ divorce. The study also found that in 1994 – often well before the divorce – these children had higher levels of anxiety, depression and anti-social behaviour than those whose parents stayed married. The study also found that child anxiety and depression increased following divorce, but in highly dysfunctional families, anti-social behaviour decreased. Parents who would eventually divorce had higher levels of depression, marital dissatisfaction and family dysfunction, which were mirrored in their children’s mental health. The author plans to study how children adjust to parental divorce over time.
Journal of Marriage and Family, December 2005, v. 67: 1286–1300. Lisa Strohschein, Department of Sociology, University of Alberta, Calgary.
Parental alcohol dependency represents a risk for maladaptive behaviours in adulthood that extend beyond alcohol dependency and into illicit drug use, according to researchers at the University of North Carolina and Arizona State University. Parental alcohol dependency has been associated with both early onset of drinking and persistent alcohol abuse throughout adulthood. The study followed 545 adolescents over 15 years, looking for differences in patterns of drug experimentation and drug use into early adulthood between children of parents with alcohol dependency and children whose parents did not have a problem with alcohol. The study found that children whose parents had a problem maintained consistent levels of drug use, such that by age 25–30, their level of drug use was substantially higher than that of children whose parents did not have a drinking problem. The study results indicate that as a consequence of parental alcohol dependency, children of these parents did not follow the typical trend by which individuals are expected to decline in drug use before age 30. In order to test mediational models, the researchers looked at marriage and its effect on declines in drug use. For all children, marriage was associated with lower levels of drug use. However, since children of parents with alcohol dependency were less likely to be married, they were more likely to have continued elevated levels of drug use in young adulthood.
Psychology of Addictive Behaviors, 2005, v. 19: 352–362. David Flora and Laurie Chassin, Department of Psychology, University of North Carolina at Chapel Hill, Department of Psychology, Arizona State University.
Some of the racial and ethnic differences underlying how adults metabolize nicotine may be apparent during adolescence, according to researchers at the Teen Tobacco Addiction Research Clinic in Baltimore, Maryland. Previous research with adults showed that black smokers take in 30 per cent more nicotine per cigarette and take longer to rid their bodies of the drug compared to white smokers. The current findings reveal that these differences are apparent during the teen years. Sixty-one white and 30 black adolescent smokers participated in the study. Researchers measured the ratio of one nicotine breakdown product to another to assess the rates at which the teens’ bodies disposed of the drug. The ratio of the two metabolites was lower among black youth, indicating that nicotine/cotinine metabolism was occurring more slowly in this group. The ratio of cotinine to the number of cigarettes smoked per day (CPD) was also examined. Although black youth smoked significantly fewer cigarettes per day – 15 cigarettes versus 20 cigarettes for white youth – white and black youth exhibited similar measures of nicotine dependence and blood cotinine concentrations. The significantly higher cotinine-to-CPD ratio among black youth confirmed the slower metabolism among black teens. These variations may influence early onset addiction to tobacco. They may also explain why certain smoking cessation therapies work better in some populations than in others, and therefore, which treatments should be offered to which teens. The findings also suggest that smoking rates may be only one of a number of factors to consider when selecting appropriate treatments.
Ethnicity and Disease, January 2006, v. 16. Eric T. Moolchan et al., National Institute on Drug Abuse, Teen Tobacco Addiction Research Clinic, Baltimore, Maryland.
Genes apparently play a bigger part for women than men in the risk of developing major depression, according to results of the largest twin study of its kind conducted through the Virginia Commonwealth University School of Medicine in Richmond, Virginia. Previous studies suggested two kinds of genetic differences between men and women: quantitative – whether the overall role of genes and environment differs – and qualitative – whether the implicated genes are the same across the sexes. In an attempt to replicate their earlier findings in a larger study, the researchers assessed data on lifetime major depression in 42,161 twins, including 15,493 complete pairs, from the national Swedish Twin Registry. They found that “the heritability of liability to major depression was significantly higher in women (42%) than in men (29%),” and that the genes that impact depression are correlated, but not identical, between the sexes. The researchers suggest there might be genes that alter the risk for depression in women in response to their hormonal environment, particularly in the postpartum period and during the premenstrual phase of the menstrual cycle. This type of depression runs in families, but men do not seem to be affected, probably because they do not have the hormonal fluctuations that women have..
American Journal of Psychiatry, January 2006, v. 163:109–114. Kenneth S. Kendler et al., Virginia Commonwealth University School of Medicine, Richmond, Virginia.
A significant proportion of young people treated for first-episode psychosis persist with substance abuse and daily tobacco use, despite being aware of the negative effects on recovery, according to researchers at the University of Melbourne. The researchers studied the course of substance abuse and daily tobacco use over 15 months among 103 individuals being treated for first-episode psychosis. At the start of the study, the rates of lifetime and 12-month substance abuse were 71 per cent and 69 per cent, respectively, with rates of daily tobacco use at 77 per cent and 76 per cent. Of participants with lifetime substance abuse, 73 per cent continued substance use, primarily cannabis, during 15-month follow-up. There was a significant reduction in the rate of any substance abuse, from 71 per cent before treatment to 53 per cent at 15 months. Participants who continued substance misuse showed a significant reduction in severity and frequency of use. Those who continued substance misuse were more likely to be younger, male and single and less likely to have completed secondary school, and to have had more severe cannabis use prior to treatment. These researchers conclude that the results demonstrate that clinicians have an opportunity early in treatment to acknowledge and reinforce these signs of behavioural change in order to reduce the risk associated with problematic substance use.
Schizophrenia Research, January 2006, v. 81: 145–150. Darryl Wade et al., Department of Psychiatry, University of Melbourne, Victoria, Australia.