Impact of ADHD and cannabis use on executive functioning in young adults

Abstract

Background Attention-deficit/hyperactivity disorder (ADHD) and cannabis use are each associated with specific cognitive deficits. Few studies have investigated the neurocognitive profile of individuals with both an ADHD history and regular cannabis use. The greatest cognitive impairment is expected among ADHD Cannabis Users compared to those with ADHD-only, Cannabis use-only, or neither. Methods Young adults (24.2±1.2 years) with a childhood ADHD diagnosis who did (n=42) and did not (n=45) report past year ≥ monthly cannabis use were compared on neuropsychological measures to a local normative comparison group (LNCG) who did (n=20) and did not (n=21) report past year regular cannabis use. Age, gender, IQ, socioeconomic status, and past year alcohol and smoking were statistical covariates. Results The ADHD group performed worse than LNCG on verbal memory, processing speed, cognitive interference, decision-making, working memory, and response inhibition. No significant effects for cannabis use emerged. Interactions between ADHD and cannabis were non-significant. Exploratory analyses revealed that individuals who began using cannabis regularly before age 16 (n=27) may have poorer executive functioning (i.e., decision-making, working memory, and response inhibition), than users who began later (n=32); replication is warranted with a larger sample. Conclusions A childhood diagnosis of ADHD, but not cannabis use in adulthood, was associated with executive dysfunction. Earlier initiation of cannabis use may be linked to poor cognitive outcomes and a significantly greater proportion of the ADHD group began using cannabis before age 16. Regular cannabis use starting after age 16 may not be sufficient to aggravate longstanding cognitive deficits characteristic of ADHD.

Age and impulsive behavior in drug addiction: A review of past research and future directions

“…Research in opioid use is more limited and has produced mixed results with a few studies showing an association with prepotent response inhibition (Constantinou et al, 2010; Forman et al, 2004; Liao et al, 2014), and this relationship was insignificant in a recent meta-analysis (Smith et al, 2014). Similar findings exist for cannabis use, although a larger body of research has been conducted, with a few studies demonstrating significant relationships (Grant et al, 2012; Hester et al, 2009; Jutras-Aswad et al, 2012; Moreno et al, 2012; Tamm et al, 2013), and again, this relationship was insignificant in the same meta-analysis (Smith at al., 2014). However, psychostimulants showed a significant association to deficits in prepotent response inhibition in the meta-analysis (Smith et al, 2014).…”

Effects of marijuana use on prefrontal and parietal volumes and cognition in emerging adults

“…Longitudinal studies have found that early MJ use initiation (prior to age 18) is related to poorer cognition, including attention, executive ability, verbal IQ, and one standard deviation reduction on full-scale IQ, even following prolonged abstinence (Tamm et al, 2013; Pope et al, 2003; Fontes et al, 2011; Meier et al, 2012). Other groups have also found that early initiation is associated with greater abnormalities.…”

A Model for Classification Based on the Functional Connectivity Pattern Dynamics of the Brain

“…Classification of brain activity patterns according to regular usage of cannabis is not only important because of the potential social impact of the explanations derived from the models learned by the classifiers, but also a challenging task from the machine learning point of view, because cannabis usage was reported to have only a minor effect in terms of conventional connectivity measures [24]. Therefore, we proposed a compound model using features based on the relative length of the DTW warping path for the classification of cannabis addiction.…”