Table 1.
Summary of Studies Examining Impact of Cannabis Use on Youth with ADHD
| Study | Number of participants by group (mean age) | Number of female participants (%) | Methodology | ADHD diagnosis & cannabis instruments (minimum cannabis use frequency for study inclusion) | Number of participants with active ADHD medication treatment | Findings related to cannabis use in ADHD population |
|---|---|---|---|---|---|---|
| Functional MRI | ||||||
| Rasmussen et al. (2016)57 | MTA: 25 ADHD+ C+ (24.6) 25 ADHD+ C− (25) 11 ADHD− C+ (24.2) 12 ADHD− C− (24.1) |
16/73 (22%) | fMRI with go/no-go task | DISC Substance Use Questionnaire (at least monthly) |
2/25 ADHD+ C+ 0/25 ADHD+ C− 24-hour medication abstinence prior to testing |
No main effects of cannabis use on response inhibition task performance or functional brain activation An interaction of diagnosis × cannabis was found in right hippocampus and cerebellar vermis during successful response inhibition in cannabis using controls |
| Newman et al. (2016)58 | MTA: 78 ADHD+ (24.8) 19 ADHD− C+ (24.1) 17 ADHD− C− (24.2) |
20/114 (18%) | fMRI with go/no-go task | DISC Substance Use Questionnaire (at least yearly) |
6/78 ADHD+ | Poorer go/no-go task performance was associated with thicker caudal inferior frontal gyrus This effect was not mediated by ADHD status or history of substance use |
| Kelly et al. (2017)59 | MTA: 23 ADHD+ C+ (24.7) 22 ADHD+ C− (25.3) 15 ADHD− C+ (24.5) 15 ADHD− C− (24.4) |
14/75 (19%) | fMRI with neuropsychiatry battery: Go/no-go task D-KEFS-CWI Trail Making Test-Part B Iowa Gambling Task Hopkins Verbal Learning Task |
DISC Substance Use Questionnaire Substance Use Recency Questionnaire (at least weekly) |
1/23 ADHD+ C+ 2/22 ADHD+ C− 24-hour medication abstinence prior to testing |
No cannabis use × ADHD diagnosis interactions were observed on any task Weekly cannabis use did not exacerbate underlying neuronal vulnerabilities in individuals with a childhood diagnosis of ADHD |
| Structural MRI | ||||||
| Lisdahl et al. (2016)61 | MTA: 37 ADHD+ C+ (24.3) 44 ADHD+ C− (24.6) 18 ADHD− C+ (23.6) 21 ADHD− C− (23.4) |
22/120 (18%) | Structural MRI | DISC Substance Use Questionnaire Substance Use Recency Questionnaire (at least monthly) |
4/37 ADHD+ C+ 2/44 ADHD+ C− 24-hour medication abstinence prior to testing |
Early cannabis use (age 16 and younger), compared to later use onset, in individuals with ADHD was associated with larger left nucleus accumbens and thicker right superior frontal and postcentral gyri |
| Çolak et al. (2019)62 | 13 ADHD+ C+ (16.0) 15 ADHD− C+ (15.9) 13 ADHD− C− (16.5) |
0/41 (0%) | Structural MRI | KSADS (present and lifetime versions) Self-report (at least 3 times weekly) |
Study excluded individuals who used psychoactive medications over preceding two months | Synthetic cannabinoid users with ADHD showed decreased cortical thickness in the right precentral and postcentral gyri compared to controls This finding was not seen when comparing synthetic cannabinoid users without ADHD to controls |
| Single-photon emission computer tomography | ||||||
| Amen & Waugh (1998)63 | 30 ADHD+ C+ (28) 10 ADHD+ C− (30) |
11/40 (28%) | SPECT with Conners Continuous Performance Test | Clinical Interview Self-report (at least weekly) |
One-week stimulant medication washout prior to imaging | Individuals with ADHD who used cannabis demonstrated bilateral temporal lobe hypoperfusion compared to those with ADHD who did not use cannabis |
| Silva et al. (2014)64 | 18 ADHD+ C+ (17.5) 11 ADHD+C− (16.1) 14 ADHD− C+ (18.3) 19 ADHD− C− (17.7) |
0/62 (0%) | SPECT with radioligand to evaluate dopamine transporter density in the striatum | KSADS-Epidemiological version International Neuropsychiatric Interview with urine drug screen confirmation |
All participants were treatment naive | The comorbidity of ADHD with SUD (cannabis and cocaine) in adolescents was associated with lower dopamine transporter availability |
| Neuropsychological battery without neuroimaging | ||||||
| Tamm et al. (2013)65 | MTA 42 ADHD+ C+ (24.4) 45 ADHD+ C− (24.6) 20 ADHD− C+ (23.7) 21 ADHD− C− (23.4) |
25/128 (20%) | Hopkins Verbal Learning Task Go/no-go task Iowa Gambling Task DKEFS-CWI Paced Auditory Serial Addition Test Trail-making task |
DISC Self-Report on Substance Use Questionnaire (at least monthly) |
4/42 ADHD+ C+ 2/45 ADHD+ C− 24-hour abstinence prior to testing |
For nearly every executive function task, ADHD, but not cannabis, had a clear effect No significant diagnosis × cannabis use interactions were found |
| Wallace et al. (2019)66 | 34 C+ (21.9) 38 C− (20.7) Subjects had subthreshold ADHD diagnosis. |
34/72 (47%) | Ruff 2&7 Conners Continuous Performance Test-II WAIS III Letter Number Sequencing DKEFS-CWI |
Child Behavior Checklist Customary drinking and drug use record with toxicology screen confirmation (weekly use) |
ADHD medication treatment was exclusionary | Cannabis use was associated with slower response on attention task but did not predict any of the other cognitive variables The ADHD × cannabis use interaction did not have significant impacts on attention |
| Questionnaires | ||||||
| Hollis et al. (2008)67 | 9 ADHD+ C+ (16.7) 18 ADHD+ C− (15.8) 19 ADHD− C+ (18.6) 53 ADHD− C− (17.2) |
44/99 (44%) | Schizotypal personality questionnaire Strengths and difficulties questionnaire Global Assessment of Function |
Parental account of childhood symptoms Schedules for Clinical Assessment in Neuropsychiatry (more than once or twice) |
27/27 ADHD+ | No significant impact of cannabis use on individuals with ADHD on any measures |
| Ly & Gehricke, (2013)68 | 29 ADHD+ C+ (24.7) 47 ADHD+ C− (27.9) |
20/76 (26%) | Assessment of hyperactivity and attention Pittsburgh Sleep Quality Index |
Structural Clinical Interview for DSM disorders Self-report (at least every other month) |
Not reported | Male subjects with higher rates of cannabis use showed significant correlation with number of inattentive symptoms Female subjects with higher rates of cannabis use saw correlations with decreased sleep quality |
ADHD+, ADHD diagnosis; ADHD−, no ADHD diagnosis; C+, cannabis users; C−, cannabis nonusers; DISC (Diagnostic Interview Schedule for Children-Parent Report; DKEFS-CWI, Delis-Kaplan Executive Function System Color Word Interference Task; DSM, Diagnostic and Statistical Manual of Mental Disorders; KSADS, Kiddie Schedule for Affective Disorders and Schizophrenia; MRI, magnetic resonance imaging; MTA, subjects recruited from the Multimodal Treatment Study of ADHD; SPECT, single-photon emission computerized tomography; SUD, substance use disorder; WAIS, Wechsler Adult Intelligence Scale