Attention deficit/hyperactivity disorder is often associated with the wandering minds and erratic behavior of schoolchildren, but it can have serious consequences for adults as well. A new study in the New England Journal of Medicine suggests that people with ADHD who are on medications for the condition are less likely to commit crimes.
"We found the same pattern regardless of which type of crime," said Paul Lichtenstein of the Karolinska Institutet in Stockholm, Sweden, lead author of the study.
ADHD is associated with conduct problems in children and adults, the study said. People with ADHD commonly stop taking their prescribed medications, particularly adolescents and young adults, according to the study.
ADHD medications control patients' symptoms of impulsiveness, irritability and restlessness. By helping tame impulsive urges, the drugs may be also preventing patients from engaging in illegal acts including violent behaviors, Lichtenstein said.
The study focused on Sweden. Comparisons with the United States are not straightforward, the study noted, because of differences in legal and judicial systems compared to Western Europe. The authors write that they "cannot address whether the associations would be the same in other cultures, and thus generalizations should be made with caution."
Still, the research may give an extra incentive for people who have been prescribed ADHD medications to continue taking them, Lichtenstein said. Also, it may suggest that prison populations could benefit from ADHD screening, as appropriate treatment could help reduce repeat offenses, he said.
About 4.1% of adults in the United States ages 18 to 44 have ADHD, according to the National Institutes of Health.
Lichtenstein and colleagues used data about more than 25,000 ADHD patients, using information from Swedish registers. More than half were men. The researchers were able to obtain information about these people's medications and criminal convictions from 2006 to 2009.
ADHD patients receiving medication were less likely to commit crimes than those who did not get pharmacological treatment, the researchers found. Specifically, men were 32% less likely and women were 41% less likely to have been convicted of a crime in the time period that researchers studied. It did not seem to matter whether the treatment was a stimulant or non-stimulant medication.
Researchers also looked at whether a single person would have a different likelihood of criminal behavior during treatment periods, compared to non-treatment periods. A treatment period consists of a sequence of prescriptions separated by no more than six months. In patients who had both periods of treatment and non-treatment, the risk of being convicted of a crime went up by 12% during non-treatment, the study said.
The study authors wrote, "It is possible that pharmacologic ADHD treatment helps patients to better organize their lives or contributes to enduring changes at the neuronal level." However, the study did not specifically investigate these issues.
The results must be taken with a few grains of salt. This is not a randomized, controlled trial, which is the gold standard of science, so the researchers did not have any direct control over when or how patients took their medications. Scientists don't know whether patients drank a lot of alcohol while taking the medications, or had supportive family members who collected their prescriptions.
But the study employed several methods to look closely at the data and search for other factors that could influence the connection between criminality and ADHD.
Researchers looked at criminality rates among patients who had discontinued the use of selective serotonin re-uptake inhibitors, a kind of medication for depression, and did not find a link there.
Medication is only one treatment option for attention deficit/hyperactivity disorder; behavioral interventions are also possible. Each individual should weigh the benefits and drawbacks of treatments in his or her own situation, Lichtenstein said.