Use of cocaine by heavy drinkers increases vulnerability to developing alcohol dependence: a 4-year follow-up study

The development of alcohol dependence is associated with specific individual personality traits and previous consumption of other drugs of abuse. However, there is little information on these risk factors in heavy drinkers before and after they meet the criteria for alcohol dependence. This study examined the influence of cocaine use and the role of impulsivity in the development of DSM-IV alcohol dependence in nondependent drinkers in a 4-year follow-up study.

A prospective cohort study was conducted to establish the risk factors associated with DSM-IV alcohol dependence. Four hundred seventy-one (nondependent) heavy drinkers were enrolled in a prospective study. At baseline, 280 were classified as heavy drinkers (HD) and 191 as heavy drinkers who also used cocaine (HD + Co). Clinical variables related to alcohol and cocaine use were assessed at 2 years and at the end of the 4-year follow-up period. The study was conducted from September 2001 until September 2006 in Madrid, Spain.

At the 4-year follow-up assessment, 67.9% of the HD + Co group met DSM-IV criteria for alcohol dependence compared to 13.6% of the HD group. Odds ratios for alcohol dependence were 12.3 and 7.0 for male and female cocaine users, respectively. Clinical and psychological variables related to impulsivity were associated with the development of alcohol dependence. The amount of cocaine used during follow-up was associated with a more rapid progression to alcohol dependence.

This study revealed that cocaine use or an impulsive personality in heavy drinkers increased the risk of developing DSM-IV alcohol dependence by 3.8 and 12.6 times, respectively. These results may be useful in designing new strategies for preventing the development of alcohol dependence.