Do cannabis users show neurological differences regardless of whether they have psychosis?
A study of 90 participants found that cannabis users had significantly elevated neurological soft signs compared to healthy controls, whether or not they also had psychosis, suggesting cannabis itself may affect brain circuits involved in motor and sensory integration.
Quick Facts
What This Study Found
Total NES scores were significantly higher in CUD with psychosis (20.53) and CUD without psychosis (15.93) compared to healthy controls (6.20, p<0.001). However, the two cannabis groups did not differ significantly from each other. Impairments spanned motor coordination, complex motor sequencing, sensory integration, and other neurological domains.
Key Numbers
30 CUD + psychosis (NES: 20.53); 30 CUD without psychosis (NES: 15.93); 30 healthy controls (NES: 6.20); p<0.001; impaired domains: motor coordination, motor sequencing, sensory integration
How They Did This
Cross-sectional study comparing 30 right-handed males with CUD and psychosis, 30 with CUD without psychosis, and 30 age-matched healthy controls. Neurological Evaluation Scale applied to measure neurological soft signs across all groups.
Why This Research Matters
Neurological soft signs are subtle markers of brain circuit dysfunction. Finding that cannabis users show these signs regardless of psychosis status suggests that cannabinoids may interact with brain circuits known to be involved in schizophrenia even when full psychosis has not developed.
The Bigger Picture
If cannabis use alone produces neurological signs similar to those seen in schizophrenia, it raises questions about whether chronic cannabis exposure alters shared neural pathways. This does not mean cannabis causes schizophrenia, but suggests overlapping brain circuit involvement.
What This Study Doesn't Tell Us
Small sample (30 per group). All male, right-handed participants from one Indian hospital. Cross-sectional design cannot determine if neurological signs preceded or followed cannabis use.
Questions This Raises
- ?Do neurological soft signs in cannabis users resolve with abstinence?
- ?Are these signs present before cannabis use begins, suggesting vulnerability rather than consequence?
- ?Do they predict which cannabis users will develop psychosis?
Trust & Context
- Key Stat:
- NES scores: 20.5 (CUD+psychosis), 15.9 (CUD only), 6.2 (controls)
- Evidence Grade:
- Cross-sectional study with appropriate comparison groups but small sample, single-site, and all-male design.
- Study Age:
- Published in 2021; neurological soft signs in cannabis users remain an understudied area.
- Original Title:
- Neurological Soft Signs in Cannabis Use Disorder with or without Psychosis: A Comparative Study from India.
- Published In:
- Journal of dual diagnosis, 17(4), 267-276 (2021)
- Authors:
- Parmar, Arpit, Lal, Rakesh, Sarkar, Siddharth(2), Singh Balhara, Yatan Pal
- Database ID:
- RTHC-03411
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
What are neurological soft signs?
Subtle neurological abnormalities in motor coordination, sensory integration, and complex motor sequencing that suggest underlying brain circuit dysfunction. They are not dramatic enough for a neurological diagnosis but indicate subtle processing differences.
Does cannabis cause these neurological changes?
The study found the association but cannot prove causation. It is possible that people with pre-existing neurological differences are more likely to use cannabis, or that cannabis exposure alters these brain circuits over time.
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Cite This Study
https://rethinkthc.com/research/RTHC-03411APA
Parmar, Arpit; Lal, Rakesh; Sarkar, Siddharth; Singh Balhara, Yatan Pal. (2021). Neurological Soft Signs in Cannabis Use Disorder with or without Psychosis: A Comparative Study from India.. Journal of dual diagnosis, 17(4), 267-276. https://doi.org/10.1080/15504263.2021.1979887
MLA
Parmar, Arpit, et al. "Neurological Soft Signs in Cannabis Use Disorder with or without Psychosis: A Comparative Study from India.." Journal of dual diagnosis, 2021. https://doi.org/10.1080/15504263.2021.1979887
RethinkTHC
RethinkTHC Research Database. "Neurological Soft Signs in Cannabis Use Disorder with or wit..." RTHC-03411. Retrieved from https://rethinkthc.com/research/parmar-2021-neurological-soft-signs-in
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.