Gender disparity exists even with drugs, finds a new study published in the journal Radiology.

Researchers “specifically wanted to determine” how stimulant drug abuse — a dependency on cocaine, amphetamines, and/or methamphetamine for nearly 16 years — affected men’s and women’s brains. With MRI scans, researchers could observe any structural brain differences and compare them to healthy men and women. Both groups of men and women were similar in age and gender.

The results showed after an average 13.5 months of abstinence or withdrawal, the brains of previously dependent women were worse off than both dependent and healthy men and women. Dependent women “had significantly less gray matter volume in frontal, limbic, and temporal regions of the brain” than every other group. Researchers explained these particular brain regions were “important for decision-making, emotion, reward processing, and habit formation.”

"Lower gray matter volumes in women who had been stimulant dependent were associated with more impulsivity, greater behavioral approach to reward, and also more severe drug use," Dr. Jody Tanabe, the study’s senior author and professor of radiology, vice chair of Research, and Neuroradiology Section Chief at the University of Colorado Denver School of Medicine, said in a press release.

Tanabe added these findings “may provide a clue to the biological processes underlying … stimulant abuse in men and women.”

"Compared to men, women tend to begin cocaine or amphetamine use at an earlier age, show accelerated escalation of drug use, report more difficulty quitting and, upon seeking treatment, report using larger quantities of these drugs," she said. "We hope that our findings will lead to further investigation into gender differences in substance dependence and, thus, more effective treatments."

The National Institute on Drug Abuse cites similar research that finds when it comes to cocaine and heroin, females self-administer sooner (and in larger amounts) than males. And in addition to possible brain differences, some research shows women are more susceptible to the cardiovascular effects of cocaine.

Already the option to enter a gender-specific drug rehab program is becoming increasingly available, Futures, an evidence-based treatment center in Palm Beach, Fla., found. But further research into the different ways men and women respond to drugs could make them more widely available.

To, an online resource for the top residential recovery centers, this would mean rehab programs would be better poised "to lead patients through the recovery process successfully, often shortening the time needed for recovery by enabling the patient to identify the triggers that lead to drug use and work toward overcoming the desire to abuse a drug of choice."

Source: Regner M, Tanabe J et al. Sex Differences in Gray Matter Changes and Brain-Behavior Relationships in Patients with Stimulant Dependence. Radiology. 2015.