Researchers at the University of California at Davis reported that certain cognitive deficits resulting from methamphetamine use can be recovered, although recovery takes at least a year. 

The researchers measured research subjects on their ability to direct their attention to specific tasks while ignoring distractions. They discovered that those who were recently abstinent (three weeks to six months) performed significantly worse on the cognitive test than those who had been abstinent one year or longer.

The researchers also found that longer-term methamphetamine use was associated with worse test scores, while longer-term abstinence was connected to improved test performance. The study did not find any statistical difference between those who had been abstinent at least one year and members of the non-drug using control group.

The authors concluded that cognitive functions lost due to the drug can improve after cessation of use, and the longer patients were drug-free, the more likely they are to recover their cognitive abilities.

Typical methamphetamine-related deficits include impaired ability to control or inhibit a response in order to carry out behaviors associated with long- term rewards and positive outcomes.

The research involved 65 recovering methamphetamine users who had been abstinent for a minimum of three weeks and a maximum of 10 years, and who had previously used the drug for periods ranging from 24 months to 28 years, with the median being 10 years.  A control group was also established of 33 participants who had never used methamphetamines.

The research was published online April 2009 in the Journal of Substance Abuse Treatment.