Abstract
BackgroundNeurological soft signs (NSS) are minor non-localizing neurological abnormalities that are conceptualized as neurodevelopmental markers that mediate the biological risk for psychosis. We aimed to explore the relationship between NSS and cannabis use, an environmental risk factor of psychosis.MethodsThis was a cross-sectional study in consecutively admitted patients hospitalized for first-episode psychosis. NSS were assessed by the NSS scale (23 items exploring motor coordination, motor integrative function, sensory integration, involuntary movements or posture, quality of lateralization). Presence of NSS was defined as a NSS scale total score ≥9.5. Cannabis use was ascertained with the cannabis subsection in the Composite International Diagnostic Interview.ResultsAmong 61 first-episode psychosis patients (mean age = 28.9 ± 9.4 years; male = 86.9%, antipsychotic-naïve = 75.4%), the prevalence of current cannabis use was 14.8% (heavy use = 8.2%, occasional use = 6.6%). NSS were present in 83.6% of the sample (cannabis users = 66.7% versus cannabis non-users = 85.5%, p = 0.16). The mean total NSS score was 15.3 ± 6.7, with a significant lower total NSS score in cannabis users (11.2 ± 5.6 versus 16.0 ± 6.7, p = 0.048). Differences were strongest for the “motor coordination” (p = 0.06) and “involuntary movements” (p = 0.07) sub-scores.ConclusionsThis study demonstrated a negative association between cannabis use and NSS, especially regarding motor discoordination. This finding supports the hypothesis that a strong environmental risk factor, such as cannabis, may contribute to the onset of psychosis even in the presence of lower biological and genetic vulnerability, as reflected indirectly by lower NSS scores. Nevertheless, additional studies are needed that explore this interaction further in larger samples and considering additional neurobiological and environmental risk factors.
Highlights
Neurological soft signs (NSS) are minor non-localizing neurological abnormalities determined by clinical examination [1]
For the presence/absence of NSS, defined by the threshold value of >9.5 on the NSS Scale, we performed a logistic regression with cannabis use as well as smoking, alcohol use, Positive and Negative Syndrome Scale (PANSS) positive score, PANSS negative score, PANSS disorganization score, Premorbid Adjustment Scale (PAS) total score, and Simpson Angus score as variables entered into the model
The fact that we found less motor coordination in patients with cannabis use and first-episode psychosis (FEP) strengthens our hypothesis that cannabis use might bring out psychosis risk in those individuals with less other neurobiological risk factors, as motor dysfunction, together with low intellectual quotient, was identified as one of the two strongest biological markers for schizophrenia risk in a recent meta-analysis [15]
Summary
Neurological soft signs (NSS) are minor non-localizing neurological abnormalities determined by clinical examination [1]. The relationship between cannabis and psychosis seems fairly specific to schizophrenia, as compared to other mental disorders [21, 22]. This relationship cannot be explained by potentially confounding factors, such as premorbid disorders, other types of drug use, intoxication effects, personality traits, sociodemographic markers, or intellectual ability [22]. Most individuals do not develop psychosis after cannabis use, suggesting that risk of psychosis must be modulated by other factors. Neurological soft signs (NSS) are minor non-localizing neurological abnormalities that are conceptualized as neurodevelopmental markers that mediate the biological risk for psychosis. We aimed to explore the relationship between NSS and cannabis use, an environmental risk factor of psychosis
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