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

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

Abstract

Purpose: 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).

Patients and methods: 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.

Results: 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.

Conclusion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Attention Deficit Disorder with Hyperactivity / diagnostic imaging
  • Attention Deficit Disorder with Hyperactivity / drug therapy*
  • Attention Deficit Disorder with Hyperactivity / epidemiology*
  • Attention Deficit Disorder with Hyperactivity / metabolism
  • Case-Control Studies
  • Comorbidity
  • Dopamine Plasma Membrane Transport Proteins / metabolism*
  • Humans
  • Male
  • Neostriatum / diagnostic imaging
  • Neostriatum / drug effects
  • Neostriatum / metabolism
  • Organotechnetium Compounds*
  • Self Medication*
  • Substance-Related Disorders / epidemiology*
  • Tomography, Emission-Computed, Single-Photon*
  • Tropanes*

Substances

  • Dopamine Plasma Membrane Transport Proteins
  • Organotechnetium Compounds
  • Tropanes
  • technetium Tc 99m TRODAT-1