Do cannabis users show neurological differences regardless of whether they have psychosis? | Research

The takeaway

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.

Readers interested in how cannabis affects brain function at a neurological level, and clinicians assessing subtle neurological changes in cannabis users.

NES scores: 20.5 (CUD+psychosis), 15.9 (CUD only), 6.2 (controls)

What the researchers 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.

Why it 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 numbers in context

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 the study worked

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.

What this study cannot 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.

How to read the evidence

Cross-sectional study with appropriate comparison groups but small sample, single-site, and all-male design.

When this study was published

Published in 2021; neurological soft signs in cannabis users remain an understudied area.

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.

Questions still open

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?

Common 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.

Read the original research

Neurological Soft Signs in Cannabis Use Disorder with or without Psychosis: A Comparative Study from India.

Journal of dual diagnosis, 17(4), 267-276

View on PubMed ↗Publisher’s paper ↗

Citation

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