Cannabis, cigarettes, and their co-occurring use: disentangling differences in default mode network functional connectivity
R. Wetherill, Zhuo Fang, K. Jagannathan, A. Childress, H. Rao, T. Franklin
Drug and Alcohol Dependence June 10, 2015 DOI: 10.1016/j.drugalcdep.2015.05.046 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Cross-sectional observational study Peer reviewed |
|---|---|
| Sample size | 87 |
| Population | Adults aged 20–57 with cannabis dependence, nicotine dependence, or neither |
| Topics | Cannabis Default mode network |
| Key findings | All substance-using groups showed lower default-mode network connectivity than healthy controls, with unique connectivity differences between the posterior cingulate cortex and specific brain regions across groups. |
Abstract
Background: Resting-state functional connectivity is a noninvasive, neuroimaging method for assessing neural network function. Altered functional connectivity among regions of the default-mode network have been associated with both nicotine and cannabis use; however, less is known about co-occurring cannabis and tobacco use.
Methods: We used posterior cingulate cortex (PCC) seed-based resting-state functional connectivity analyses to examine default mode network (DMN) connectivity strength differences between four groups: 1) individuals diagnosed with cannabis dependence who do not smoke tobacco (n=19; ages 20–50), 2) cannabis-dependent individuals who smoke tobacco (n=23, ages 21–52), 3) cannabis-naïve, nicotine-dependent individuals who smoke tobacco (n=24, ages 21–57), and 4) cannabis- and tobacco-naïve healthy controls (n=21, ages 21–50), controlling for age, sex, and alcohol use. We also explored associations between connectivity strength and measures of cannabis and tobacco use.
Results: PCC seed-based analyses identified the core nodes of the DMN (i.e., PCC, medial prefrontal cortex, inferior parietal cortex, and temporal cortex). In general, the cannabis-dependent, nicotine-dependent, and co-occurring use groups showed lower DMN connectivity strengths than controls, with unique group differences in connectivity strength between the PCC and the cerebellum, medial prefrontal cortex, parahippocampus, and anterior insula. In cannabis-dependent individuals, PCC-right anterior insula connectivity strength correlated with duration of cannabis use.
Conclusions: This study extends previous research that independently examined the differences in resting-state functional connectivity among individuals who smoke cannabis and tobacco by including an examination of co-occurring cannabis and tobacco use and provides further evidence that cannabis and tobacco exposure is associated with alterations in DMN connectivity.