Exposing adolescent rats to THC
(tetrahydrocannabinol) – the primary psychoactive ingredient in marijuana – can
lead to molecular and behavioural alterations in the next generation of
offspring, even though progeny were not directly exposed to the drug,
researchers at the Icahn School of Medicine at Mount Sinai have found.
Male offspring showed stronger motivation
to self-administer heroin during their adulthood and molecular changes in the
glutamatergic system, which is the most important excitatory pathway for
neurotransmission in the brain.
Damage in the glutamate pathway, which
regulates synaptic plasticity, has been linked to disturbances in goal-directed
behaviour and habit formation.
"Our study emphasises that cannabis
[marijuana] affects not just those exposed, but has adverse affects on future
generations," said Yasmin Hurd, PhD, the study's senior author, and
professor of psychiatry and neuroscience at the Icahn School of Medicine at
"Finding increased vulnerability to drug
addiction and compulsive behaviour in generations not directly exposed is an
important consideration for legislators considering legalising marijuana."
In the study, Dr Hurd and colleagues gave
adolescent male rats 1.5 mg/kg of THC, similar to about one joint in human use.
None of the rats had been exposed to THC
before, but their parents were exposed to THC as teens and then mated later in
life. THC-exposed offspring worked harder to self-administer heroin by pressing
a lever multiple times to get heroin infusion.
Although marijuana use and safety tends to
be discussed in terms of its impact to the individual during the lifetime, few
studies have addressed adverse effects in future generations. "What this
opens up are many questions regarding the epigenetic mechanisms that mediate
cross-generational brain effects," said Dr Hurd.
Future studies are now being explored to
determine whether THC effects continue to be transmitted to even the subsequent
grandchildren and great-grandchildren generations.
Another important question relates to
potential treatment interventions in order to reverse the cross-generational
THC effects. Such insights could also have implications for novel treatment
opportunities for related psychiatric illnesses.
Marijuana use triggers psychosis
Marijuana not harmless to adolescents