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The rate of attention deficit hyperactivity disorder (ADHD) among illicit users of psychostimulants is roughly nine times higher than normal, a new study estimates.
Almost half of illicit psychostimulant users showed evidence of ADHD, compared to an estimated rate of no more than 6% in adults in general, the Australian researchers found.
Dr. Sharlene Kaye, who led the study, told Reuters Health by email that the findings "highlight the need for clinicians treating people with substance use disorders to consider, and ideally screen for, ADHD as a potentially comorbid condition that, unidentified and untreated, can worsen treatment response and prognosis for recovery."
In a December online paper in Addiction, Dr. Kaye and colleagues at the University of New South Wales, Sydney note that ADHD is a significant risk factor for the development of alcohol and illicit drug use disorders in adolescence and adulthood and is consistently over-represented among substance use disorder populations.
Estimates suggest it may affect up to 10% of children and 23% of those engaged in substance misuse.
How the study was done
To investigate further, the researcher studied 269 regular users of methamphetamine or cocaine or both. All had used illicit psychostimulants at least weekly for 12 months.
In fact, 71% had used them more than three times per week over this period, and 88% met criteria for psychostimulant dependence.
Their age ranged from 19 to 62 years, with an average of 35.6. Most (86%) had been treated for substance dependence. Half (52%) were in treatment at the time of the interview and most (88%) were unemployed.
In all, 45% screened positive for adult ADHD. Symptoms of inattention (90%) were more prevalent than those of hyperactivity/impulsivity (57%). Only 17% had received a prior diagnosis of ADHD, and 14% were subsequently treated for it.
This, say the investigators, "may in part, reflect the fact that the sample was aged in their mid-thirties, and the level of awareness and diagnosis of ADHD in their childhood years was far lower than it is today."
The findings
Of the positive group, 88% reported that their symptoms were unrelated to drug use and were consistent with their usual behaviour.
After controlling for other factors, ADHD was independently associated with fewer years of education, earlier initiation of regular tobacco use and more extensive lifetime polydrug use.
Only one patient was currently being treated for ADHD with a stimulant medication. The investigators observe that although the first line of treatment is usually stimulant medication such as methylphenidate, these may be contraindicated among substance abusers and extended-release formulations or nonstimulant medications may be more appropriate.
"Identification of comorbid ADHD," the researchers point out "may assist in planning appropriate forms of substance abuse treatment that will reduce the risk of noncompliance with treatment regimens and protocols due to symptoms such as inattention, impulsivity and disorganization."
Overall, they conclude that recognizing the high risk of ADHD in patients seeking drug abuse treatment is important because left undiagnosed and untreated, ADHD may have an impact on "treatment compliance, retention and outcome."
(David Douglas, Reuters Health, December 2012)
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