Women’s Brains

New research indicates women who abuse stimulants experience critical, long-term decrease in brain volume as well as changes that affect crucial emotional and decision-making abilities — even after extended periods of abstinence from drug use. 

Men who abuse stimulants, on the other hand, undergo no significant brain volume changes.

Those findings are reported in a new study released online today in the journal Radiology, published by the Radiological Society of North America. 

The study notes that even more than one year after abstaining from stimulant drug use, MRIs revealed that women’s gray matter shrank greatly and showed vast changes in the brain structures involved in reward, learning, and the control of behavioral and organizational functions. 

“We found that after an average of 13.5 months of abstinence, women who were previously dependent on stimulants had significantly less gray matter volume in several brain areas compared with healthy women,” said the study's senior author, Dr. Jody Tanabe, professor of radiology, vice chair of research, and neuroradiology section chief at the University of Colorado School of Medicine. “These brain areas are important for decision making, emotion, reward processing, and habit formation.”

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How Brains Differ

Tanabe and her colleagues wanted to discover how the brains of people previously dependent on stimulants differed from the brains of healthy people. 

“We specifically wanted to determine how these brain effects differed by [sex],” she said. “While women previously dependent on stimulants demonstrated widespread brain differences when compared with their healthy control counterparts, men demonstrated no significant brain differences.” 

Substance Abuse

The team analyzed MRI exams in 127 men and women. These included 59 people (28 women and 31 men) who were previously dependent on cocaine, amphetamines, and/or methamphetamine for an average of 15.7 years as well as 68 healthy people (28 women and 40 men). 

The researchers do not know why brain volume changes.

Tanabe’s colleague Dr. Michael Regner, radiology resident at the University of Colorado Denver School of Medicine, Ph.D. graduate student, and lead author of the study, said, “We do not know if the smaller gray matter volume was a result of stimulant dependence, or if the smaller gray matter differences contributed to the development of stimulant dependence. Since the brain consists of numerous cells and the spaces between cells, we do not know if some of the cells die, become smaller, or if the spaces between the cells becomes smaller.” 

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What Less Gray Matter Might Mean

The researchers also wanted to know how behaviors might affect brain volume. They discovered that lower gray matter volumes correlated with the subjects’ tendencies to seek reward and novelty. 

“Lower volumes in women who had been stimulant-dependent were associated with more impulsivity, greater behavioral approach to reward, and also more severe drug use,” Tanabe said. “The men and healthy women we studied did not show such correlations.” 

The results may provide a clue to the biological processes that underlie stimulant abuse in men and women, she added. 

The ages at which men and women first use stimulant drugs may provide clues to the differences between the sexes observed in the study. Previous studies, Regner said, have reported a tendency for women to begin using cocaine or stimulants at an earlier age.

However, in this latest study, there were no significant differences between the age of first use in men and women. 

Women began using stimulants between the ages of 10 and 44. The average age of first use in women was 18 years. Men began using stimulants between the ages of 11 and 24. Their average age of first use was 16.6 years.

Regner offered a possible reason the team did not see a difference in the age of first use. The study participants, he said, were all residents of a substance-dependence treatment program, and many had been referred to the program by the court system.

“Our subjects had severe substance dependence,” Regner said.

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Starting Younger Makes It Harder to Quit

Tanabe said women who begin using stimulants at a younger age “show accelerated escalation of drug use and report more difficulty quitting. Upon seeking treatment, they also report using larger quantities of these drugs. We hope our findings lead to further investigation into gender differences in substance dependence, and more effective treatments.”

Are the brain volume changes permanent? 

“We do not know if these brain changes predate the first use of a drug, develop during drug dependence, or result from abstinence,” Regner said. “The brain changes we observed are likely some combination of all of these.” 

Research by other scientists shows that “there is some degree of ‘recovery,’ and that our brains are quite dynamic,” Regner said. “However, the field does not yet have robust longitudinal studies to demonstrate how the brain changes over time from first use to dependence to long-term abstinence.”