In childhood, ADHD is often associated with significant oppositional behavior.
And, these behavior problems frequently escalate into more serious conduct
disturbance and criminal behavior during adolescence and adulthood. Although
medication treatment for ADHD has been shown to yield benefits in many areas of
individual’s functioning, the impact of treatment on adult criminal behavior
has not been carefully investigated. This is an important omission in the
The New England Journal of Medicine recently published an excellent
study on this issue. As discussed below, results from this study strongly
suggest that medication treatment reduces criminality in adults with ADHD
[Lichtenstein et al., (2012) Medication for Attention Deficit-Hyperactivity
Disorder and Criminality, New England Journal of Medicine, 367,
The study was conducted in Sweden where national data bases that track
psychiatric diagnoses, ADHD prescriptions, and criminal convictions make it
ideal for conducting a large, population-based investigation of this question.
The authors began by identifying over 25,500 individuals born before 1990 who
had a recorded diagnosis of ADHD in the National Patient Register; over 9,000
were female. Comparison subjects for each participant were identified from a
population data base that enabled researchers to match them on age, sex, and
For all participants, convictions for criminal offenses between 2006 and 2009
were identified using a national crime data base. During this period, members
of the sample ranged from 15 to more than 40 years old.
Information on subjects’ medication treatment during this 3-year period was
obtained using the Prescribed Drug Register, a national data base that tracks
all medication prescriptions in Sweden. Individuals were considered to be
receiving medication treatment during the time interval between two
prescriptions for ADHD medication, as long as those prescriptions were less
than 6 months apart.
For example, if an individual filled a prescription at Time 1 and a second
prescription 3 months later at Time 2, the interval between Time 1 and Time 2
was considered a treatment period. If that same individual did not fill a third
prescription until 7 months later, the interval between Time 2 and Time 3 would
be consider a nontreatment period.
Nearly 40% of women and 50% of men with ADHD never received ADHD medication
between 2006 and 2009; fewer than 5% of each gender were treated continuously.
The remaining participants had both treatment and nontreatment periods using
the definition provided above.
Question 1 – Are rates of criminal convictions higher among adults with ADHD
than comparison adults?
The answer to this question was distressingly clear. Among males, 36.6% were
convicted of at least one crime between 2006-2009 compared to less than 9% of
comparison males. Among females, the corresponding percentages were 15.4% and
Question 2 – Does ADHD medication treatment reduce criminal behavior in
individuals with ADHD?
The researchers examined this question in two ways. First, they compared rates
of criminal behavior that occurred during all treatment and nontreatment
periods across all participants with ADHD. For men, the analysis was based on
over 56,000 periods. For women, it was based on over 23,500 periods. By
comparing prescription dates for each individual with dates that they engaged
in criminal behavior, the researchers determined whether crimes occurred during
treatment or nontreatment periods. (Note – The number of treatment and
nontreatment periods is greater than the number of participants because each
participant could have multiple treatment and nontreatment periods depending on
how often they started and stopped medication.)
The results were clear – during treatment periods, the likelihood of being
convicted of a crime was approximately 30% lower for men and 22% lower for
Within Person Analyses
One limitation with the above analysis is that the treatment and nontreatment
comparisons are made across different individuals. Individuals who consistently
use medication may differ in important ways from those who do not, and these
differences may better explain the different rates of criminal behavior than
medication treatment per se.
To address this potential confound, the researchers adopted the clever solution
of comparing the rates of criminal behavior in the same individuals during
treatment and nontreatment periods. Thus, in this analysis, each person
essentially serves as his or her own control. With this approach, if rates of
criminal behavior differ based on whether medication treatment is currently in
place, it is more likely to reflect an actual medication effect rather than
reflecting other differences between individuals who are more vs. less likely
to use medication.
Using this method, rates of criminal behavior were 32% lower in men during
treatment periods compared to nontreatment periods; in women, the reduction was
41%. Follow up analyses indicated that these reductions held whether the
transition was from a medication to a nonmedication period or the other way
around. And, similar reductions were found regardless of whether the initial or
subsequent episodes of medication treatment were considered.
Finally, the authors tested whether findings were specific to ADHD medication,
or also occurred for other psychiatric drugs that individuals with ADHD were
prescribed; this analysis focus on the use of SSRIs, a class of drugs commonly
used to treat depression and anxiety. In contrast results found for ADHD
medication, there was no evidence of any association between SSRI treatment and
criminal behavior in adults with ADHD.
Question 3 – Is there a long-term effect of ADHD medication treatment on
The analyses presented above suggest that criminal behavior is less likely to
occur during periods when ADHD medication treatment is in place. Another
important question is whether medication treatment provides any long-term
protective effect against criminal behavior.
To examine this question, the authors tested whether medication treatment
status on January 1, 2006 – the start of the 3-year window – predicted rates of
criminal behavior during 2009. If medication treatment provided long-term
protective benefits, than those in treatment on this start date should have
lower rates of criminal behavior in 2009 than those not in treatment. There was
no evidence that this was the case.
Summary and Implications
Results from this study provide strong evidence that medication treatment for
ADHD reduces the risk of criminal behavior in adults during periods when
treatment is in place. However, there was no evidence that treatment provides a
long-term protective benefit. This is consistent with much of the literature on
ADHD medication treatment, i.e., whatever benefits accrue typically do not
persist significantly beyond the termination of treatment.
Strengths of this study include a large and nationally representative sample;
this provides great confidence in the results that were obtained. The authors
were also careful to rule out that factors other than ADHD medication treatment
that could explain the reduction in criminal behavior that was evident during
treatment periods. This included using within person analyses, testing whether
the order of change of medication status mattered (it did not), and whether
similar effects were found for a different class of psychiatric medication
(they were not).
While these are important strengths, the authors recognize that because this
was not a randomized controlled trial, all possible confounding factors cannot
be conclusively eliminated. However, a randomized controlled trial could not be
conducted as it would be unethical and impossible to randomly assign groups of
adults with ADHD to take or not take medication for such an extended period.
Thus, a study like the one reported here represents the about the best that one
No information was provided on why medication may yield reduced criminal
behavior. One explanation is that adults’ overall functioning was better when
taking medication, and this reduces their engaging in criminal acts. Because
many criminal acts result from impulsive behavior, the reduction in impulsivity
that medication is likely to produce could also be a contributing factor.
The authors note that because there study took place in Sweden, caution is
required about assuming similar findings would occur in the US and elsewhere.
However, there is no particular reason to assume that the results are unique to
Sweden, as Sweden does not appear to be unusual in its rates of ADHD or ADHD
Finally, it should be noted that the authors did not consider whether
nonmedical treatments for ADHD might have a similar impact on criminal
behavior. For example, cognitive-behavioral treatment has been shown to be
helpful to adults with ADHD and may yield similar, or even greater, reductions
in criminal behavior. And, it is possible that such treatment could have more
enduring effects since new skills are being learned. This would be an important
question to examine in subsequent research; in the meantime, one should not
assume that medication is the only way to obtain the benefits reported here.
In summary, results suggest that medication treatment for ADHD significantly
lowers the rate of criminal behavior in adults with the disorder. However,
there is no evidence that medication treatment conveys benefits that extend
beyond the time that it is in place. These are important factors to consider in
treatment planning for adults with ADHD, particularly those with a history of
antisocial behavior. In future research, it would be beneficial to investigate
whether psychosocial treatments can provide similar benefits.