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Clin Nucl Med. 2014 Feb;39(2):e129-34. doi: 10.1097/RLU.0b013e31829f9119.

Searching for a neurobiological basis for self-medication theory in ADHD comorbid with substance use disorders: an in vivo study of dopamine transporters using (99m)Tc-TRODAT-1 SPECT.

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From the *Laboratório de Medicina Nuclear do Complexo Hospitalar Santa Casa (LAMENU), Porto Alegre; †ADHD Outpatient Program, Child and Adolescent Psychiatric Division (PRODAH), Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre; ‡Laboratório Interdisciplinar de Neurociências Clínicas (LiNC), Department of Psychiatry, Universidade Federal de São Paulo (UNIFESP), São Paulo; §Center for Drug and Alcohol Research, HCPA, Universidade Federal do RGS (UFRGS), Porto Alegre; ¶Universidade Luterana do Brasil, Porto Alegre; and ∥Instituto Nacional de Psiquiatria do Desenvolvimento, Porto Alegre, Brazil.



Attention-deficit/hyperactivity disorder (ADHD) and substance use disorders (SUD) frequently co-occur. Although several studies have shown changes in striatal dopamine transporter (DAT) density in these disorders, little is known about the neurobiological basis of the comorbidity. The aim of this study was to evaluate striatal DAT density in treatment-naive ADHD adolescents with SUD (ADHD + SUD) and without SUD (ADHD), compared to SUD adolescents without ADHD (SUD) and healthy control subjects (HC).


Sixty-two male age-matched subjects diagnosed with DSM-IV criteria were included: ADHD + SUD (n = 18), SUD (n = 14), HC (n = 19), and ADHD (n = 11). Urine tests confirmed participants' drug use. All subjects performed SPECT scans with Tc-TRODAT-1 to evaluate DAT density in the striatum.


The mean right striatum specific binding were 1.68 (ADHD), 1.38 (ADHD + SUD), 1.19 (HC), 1.17 (SUD), and in left striatum 1.65 (ADHD), 1.39 (ADHD + SUD), 1.19 (HC), and 1.17 (SUD). The ADHD group presented significantly higher striatal DAT density compared with ADHD + SUD, SUD, and HC groups. Adolescents with ADHD + SUD had significantly lower DAT density than those with ADHD, but significantly higher DAT density than those with SUD only and no significant difference from the healthy control group.


The ADHD + SUD group had lower striatal DAT density in comparison with ADHD without SUD. It is possible to speculate that the use of cannabis and cocaine is responsible for the lower striatal DAT density in this group which would help in understanding the neurobiological basis for the self-medication theory in ADHD adolescents.

[Indexed for MEDLINE]

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