psychiatrysource.com, 27 October
Researchers have found altered neural
synchronization in people who smoke cannabis, providing
evidence to support the link between the use of this drug
Altered neural synchronization has previously been
demonstrated in patients with schizophrenia. This led
Patrick Skosnik ( Indiana University , Bloomington , USA )
and team to suggest that such alterations may represent a
neurophysiological link between schizophrenia symptoms and
the neurobehavioral effects of cannabis.
The researchers assessed neural synchronization using
electroencephalograms (EEG) to measure auditory
steady-state potentials, eg, auditory click trains at
specific frequencies – 20, 30, and 40 Hz – in 17 cannabis
users and 16 drug naïve individuals.
The cannabis users showed decreased EEG power and
signal-to-noise ratio at the stimulation frequency of 20
Hz compared with non-drug users.
Skosnik and colleagues note that there was no significant
difference between the two groups with regard to noise
power, indicating that the altered neural synchronization
in cannabis users was due to decreased signal strength of
oscillating circuits and not the increased noise stemming
from neural background activity.
The cannabis users also demonstrated increased schizotypal
personality characteristics, as assessed on the
Schizotypal Personality Questionnaire, compared with
controls. However, there was no significant difference
between the two groups in scores on the Wechsler Adult
Intelligence Scale. This demonstrates that any alterations
in neural synchrony were not associated with generalized
cognitive or sensory deficits, the researchers note.
Further analysis revealed that scores on the Schizotypal
Personality Questionnaire positively correlated with total
years of cannabis use. In addition, schizotypy scores
negatively correlated with 20 Hz power, indicating that
cannabis-using individuals scoring higher in schizotypy
had larger deficits in neural synchronization.
"These data provide evidence for neural synchronization
and early-stage sensory processing deficits in cannabis
use," the team writes in the American Journal of
"Given that there is tight coupling of the endocannabinoid
and dopamine systems, it appears possible that genetic
anomalies leading to altered dopamine activity may
interact with early cannabis exposure to produce overt
Am J Psychiatry 2006;