Table 3.
Clinical studies evaluating neural and cognitive effects of marijuana use in PLWH
| Methods/Measures Used | Participants | Primary Findings | |
|---|---|---|---|
| Brain Imaging Studies | |||
| Thames et. al. 2017 | Structural MRI | 77 participants across 4 groups: 16 MJ−/HIV−13 MJ+/HIV− 24 MJ−/HIV+ 24 MJ+/HIV+ |
Greater cannabis use (grams/week) was associated with smaller entorhinal and fusiform cortical volumes, while HIV status was associated with thinner cingulate cortices. No interactive or additive effect of cannabis use and HIV infection was observed in brain structure. |
| Meade et. al. 2018 | Functional MRI-Counting Stroop task | 93 participants across 4 groups: 25 MJ−/HIV− 19 MJ+/HIV− 29 MJ−/HIV+ 20 MJ+/HIV+ |
Both cannabis use and HIV status were independently associated with abnormalities in brain activation, with greater parietal activation bilaterally in the cannabis users and greater anterior cingulate cortex activation in the HIV(+) participants. Across the 4 groups, HIV(+) cannabis users showed the greatest activation in the insular region, suggesting an additive effect. During the counting Stroop task, insular activation (BOLD signal change) was greater with more years of regular marijuana use, especially in the HIV(+) group. |
| Chang et. al. 2006a | 1H MRS (localized spectroscopy in 6 brain regions) | 96 participants across 4 groups: 30 MJ−/HIV− 24 MJ+/HIV− 21 MJ−/HIV+ 21MJ+/HIV+ |
Cannabis use was associated with lower levels of neuronal metabolites (NAA, choline-compounds and glutamate) in the basal ganglia, but higher glial metabolite (total creatine) levels in the thalamus. HIV was associated with trends for lower NAA levels in the parietal white matter and higher choline-compound levels in the basal ganglia. However, HIV+/MJ+ group had normalization of the low glutamate levels in frontal white matter that were observed in HIV+/MJ− and HIV−/MJ+ groups. |
| Cognitive Studies | |||
| Gonzalez et. al. 2011 | Procedural learning | 86 participants across 4 groups: 21 MJ−/HIV− 23 MJ+/HIV− 25 MJ−/HIV+ 17 MJ+/HIV+ |
Among participants with a history of polysubstance use, HIV status and cannabis dependence (CD) were both independently associated with poorer task performance. While interaction effects were not observed, there was also evidence for additive adverse effects of HIV and CD on task performance. |
| Skalski et. al. 2018 | Learning, memory, executive function, processing speed, motor function, verbal fluency, attention/working memory | 69 HIV(+) participants: 12 early onset cannabis users 15 late onset cannabis users 42 non-users |
Early onset cannabis users (regular use prior to age 18), compared to non-users and late onset users (regular use at age 18 or later), were more likely to have memory and learning impairment. |
| Chang et. al. 2006a | Gross motor function, verbal memory, fine motor speed, executive function, verbal intelligence, mood, psychomotor speed | 96 participants across 4 groups: 30 MJ−/HIV− 24 MJ+/HIV− 21 MJ−/HIV+ 21 MJ+/HIV+ |
After controlling for age, education, and mood differences, cannabis users did not perform differently from non-users on neuropsychological testing and HIV(+) individuals were slower on some reaction times. No interactive effects between HIV status and cannabis use were observed. |
| Lorkiewicz et. al. 2018 | Memory, attention, self-reported cognitive function | 215 HIV(+) participants diagnosed with substance dependence or injection drug use | Current cannabis use was associated with poorer self-reported cognitive function. |
| Thames et. al. 2016 | Premorbid intellectual ability, attention/working memory, processing speed, verbal fluency, learning, memory, executive functioning | 89 participants across 6 groups: 12 MJ−/HIV− 14 MJ−/HIV+ 12 MJ+ light/HIV− 30 MJ+ light/HIV+ 10 MJ+ moderate/HIV− 11 MJ+ moderate/HIV+ |
Both HIV status and moderate-to-heavy MJ use were associated with poorer test performance. Moderate-to-heavy MJ users performed worse for processing speed, learning/memory, and executive functioning compared to light users and non-users. HIV(+) individuals performed poorer for learning/memory, and executive functioning compared to HIV(−) individuals. There was an interactive effect on learning and memory with HIV(+) moderate-to-heavy users having the poorest learning and memory of all the groups. An interactive effect was observed on verbal fluency: HIV(+) light users performed better that HIV(−) light users. |
| Thames et. al. 2017 | Premorbid intellectual ability, attention/working memory, processing speed, verbal fluency, learning, memory, executive functioning | 77 participants across 4 groups: 16 MJ−/HIV− 13 MJ+/HIV− 24 MJ−/HIV+ 24 MJ+/HIV+ |
An interaction between cannabis use and HIV-status was observed. More MJ use was associated with lower global cognitive scores in HIV(−) controls but not in HIV(+) participants. In light MJ users, the HIV(−) group displayed better global cognitive performance than the HIV(+) group. In heavier MJ users, global performance did not differ by HIV status. Processing speed and memory measures drove this effect. |
| Cristiani et. al. 2004 | Intelligence, learning, memory, verbal reasoning, executive functioning, verbal fluency, figure fluency, motor skills, attention/working memory, processing speed | 282 participants across 6 groups: 25 MJ−/HIV− 49 MJ+/HIV− 48 MJ−/asymptomatic HIV+ 79 MJ+/asymptomatic HIV+ 32 MJ−/symptomatic HIV+ 55 MJ+/symptomatic HIV+ |
MJ use was associated with greater cognitive impairment in persons with symptomatic HIV infection, but these effects were not evident in HIV(−) participants or participants with asymptomatic HIV infection. These overall effects appeared to be driven by performance on delayed memory tasks. The effect of marijuana use was greatest in the symptomatic HIV(+) group. |