RESUMO
PURPOSE: Alcohol is believed to have pain-dampening effects and is often used as self-medication by persons with pain problems; however, experimental evidence confirming this effect is scarce. We conducted a systematic review of experimental studies on the effects of nonrecurring alcohol administration on pain perception in healthy human subjects and the underlying mechanisms. METHOD: Three databases (PubMed, PsycINFO, and Web of Science) were searched for relevant studies using a predefined algorithm. In a next step, irrelevant articles were excluded by screening titles and abstracts. Finally, articles were checked regarding a set of methodological criteria; only publications meeting these criteria were selected for this review. A total of 14 experimental studies were identified. RESULTS: Overall, most of the studies were able to show a pain-dampening effect of alcohol. However, many of them had methodological shortcomings (eg, lack of placebo control, insufficient blinding, or very small sample sizes). In addition, comparability is limited due to considerable variations in alcohol administration and pain measurement. More importantly, potential mechanisms of action and moderating variables have scarcely been investigated. CONCLUSION: Despite the frequent use of alcohol as self-medication by persons with pain problems, there are to date only a few experimental investigations of alcohol effects on pain perceptions. The results of these studies suggest that alcohol does in fact have pain-dampening effects. However, the mechanisms implicated in these effects are still unknown, and experimental research has been limited to pain-free subjects. Future research should provide more knowledge about alcohol effects on pain, especially in chronic pain patients.
RESUMO
The neurotrophic growth factor brain derived neurotrophic factor (BDNF) was linked to the risk of alcohol relapse in clinical studies. In this study we investigated alterations in the methylation of the BDNF gene during alcohol withdrawal (day 1, 7 and 14) in 99 male alcohol-dependent patients compared to age matched healthy males (n=33). In particular, we aimed to investigate a possible association between the BDNF promoter methylation and the self-reported duration of alcohol abstinence before relapse. Mean methylation of the BDNF promoter was significantly increased in alcohol-dependent patients compared to the healthy controls (F=10.014, p<0.001) and decreased significantly during alcohol-withdrawal (F=10.014, p<0.001). Moreover, mean methylation was associated with depressive (F=2.014, p<0.001) and anxious symptoms in the alcohol-dependent patients (F=2.228, p<0.001). On day 14 of alcohol-withdrawal we found significantly higher methylation rates in those patients who abstained longer before relapse compared to those patients who abstained shorter (F=9.938, p<0.001). Our results suggest an association between BDNF expression and the symptomatology of alcohol withdrawal and imply that changes in the methylation of the BDNF IV gene may contribute to alcohol consumption.