Past Cannabis Use Linked to Different Hippocampal Shape Changes in Healthy People vs. Schizophrenia
People with a past cannabis use disorder showed distinct hippocampal shape changes whether they had schizophrenia or not, with healthy cannabis users' changes linked to memory problems and schizophrenia cannabis users' changes linked to longer use duration.
Quick Facts
What This Study Found
Researchers compared hippocampal shape in four groups: healthy controls (n=44), healthy controls with past cannabis use disorder (n=10), schizophrenia without substance history (n=28), and schizophrenia with past cannabis use disorder (n=15).
Both cannabis-using groups showed distinct hippocampal shape differences from their respective non-using counterparts, but the patterns differed. In healthy cannabis users, shape changes correlated with poorer episodic memory performance. In schizophrenia cannabis users, shape changes correlated with longer duration of cannabis use and shorter duration of remission.
This suggests cannabis-related hippocampal changes have different functional consequences depending on whether someone has schizophrenia.
Key Numbers
44 healthy controls; 10 healthy with past CUD; 28 schizophrenia without substance use; 15 schizophrenia with past CUD; distinct hippocampal shape patterns in each cannabis-using group
How They Did This
Cross-sectional MRI study with four demographically matched groups. Large-deformation, high-dimensional brain mapping produced surface-based hippocampal representations. Correlated morphological differences with episodic memory and cannabis use history.
Why This Research Matters
The hippocampus is central to memory formation and is affected by both cannabis and schizophrenia. Finding that cannabis-related hippocampal changes differ between healthy and schizophrenia populations suggests the underlying neurobiology differs.
The Bigger Picture
Cannabis effects on the brain may not be uniform across populations. People with schizophrenia may be uniquely vulnerable to certain cannabis-related brain changes, which could explain why cannabis use is particularly harmful in this population.
What This Study Doesn't Tell Us
Small groups (especially n=10 for healthy cannabis users). Past, not current, cannabis use studied. Cross-sectional design cannot determine whether hippocampal differences preceded or followed cannabis use. Shape changes do not reveal cellular mechanisms.
Questions This Raises
- ?Do hippocampal shape changes reverse with prolonged abstinence?
- ?Are these changes markers of vulnerability or consequences of use?
- ?Would longer-duration cannabis use in healthy people eventually produce the schizophrenia-like pattern?
Trust & Context
- Key Stat:
- Different hippocampal shape changes in healthy vs. schizophrenia cannabis users
- Evidence Grade:
- Sophisticated neuroimaging with four well-matched groups, but small sample sizes limit statistical power and generalizability.
- Study Age:
- Published in 2015. Brain imaging of cannabis effects has become more refined.
- Original Title:
- Cannabis-related episodic memory deficits and hippocampal morphological differences in healthy individuals and schizophrenia subjects.
- Published In:
- Hippocampus, 25(9), 1042-51 (2015)
- Authors:
- Smith, Matthew J, Cobia, Derin J, Reilly, James L, Gilman, Jodi M, Roberts, Andrea G, Alpert, Kathryn I, Wang, Lei, Breiter, Hans C, Csernansky, John G
- Database ID:
- RTHC-01062
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does cannabis change the shape of the hippocampus?
This study found that past cannabis use disorder was associated with distinct hippocampal shape differences in both healthy people and those with schizophrenia. However, the patterns were different in each group, suggesting the impact depends on underlying brain health.
Does cannabis affect memory through hippocampal changes?
In healthy people with past cannabis use disorder, hippocampal shape changes correlated with poorer episodic memory. This supports a link between cannabis-related structural changes and memory function, though causation cannot be established from this design.
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Cite This Study
https://rethinkthc.com/research/RTHC-01062APA
Smith, Matthew J; Cobia, Derin J; Reilly, James L; Gilman, Jodi M; Roberts, Andrea G; Alpert, Kathryn I; Wang, Lei; Breiter, Hans C; Csernansky, John G. (2015). Cannabis-related episodic memory deficits and hippocampal morphological differences in healthy individuals and schizophrenia subjects.. Hippocampus, 25(9), 1042-51. https://doi.org/10.1002/hipo.22427
MLA
Smith, Matthew J, et al. "Cannabis-related episodic memory deficits and hippocampal morphological differences in healthy individuals and schizophrenia subjects.." Hippocampus, 2015. https://doi.org/10.1002/hipo.22427
RethinkTHC
RethinkTHC Research Database. "Cannabis-related episodic memory deficits and hippocampal mo..." RTHC-01062. Retrieved from https://rethinkthc.com/research/smith-2015-cannabisrelated-episodic-memory-deficits
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.