Marijuana and the Brain

After you inhale marijuana smoke, its chemicals are distributed throughout the body.
THC is a very potent chemical compared to other psychoactive drugs. An intravenous (IV) dose of only 1 milligram can produce serious mental and psychological effects. Once in your bloodstream, THC typically reaches the brain within seconds after it is inhaled and begins to go to work.
Marijuana users often describe the experience of smoking marijuana as initially relaxing and mellow, creating a feeling of haziness and light-headedness. The user's eyes may dilate, causing colors to appear more intense, and other senses may be enhanced. Later, feelings of a paranoia and panic may be felt by the user. The interaction of the THC with the brain is what causes these feelings. To understand how marijuana affects the brain, you need to know about the parts of the brain that are affected by THC. Here are the basics:
  • Neurons are the cells that process information in the brain. Chemicals called neurotransmitters allow neurons to communicate with each other.
  • Neurotransmitters fill the gap, or synapse, between two neurons and bind to protein receptors, which enable various functions and allow the brain and body to be turned on and off.
  • Some neurons have thousands of receptors that are specific to particular neurotransmitters.
  • Foreign chemicals, like THC, can mimic or block actions of neurotransmitters and interfere with normal functions.
In your brain, there are groups of cannabinoid receptors concentrated in several different places. These cannabinoid receptors have an effect on several mental and physical activities, including:
  • Short-term memory
  • Coordination
  • Learning
  • Problem solving
Cannabinoid receptors are activated by a neurotransmitter called anandamide. Anandamide belongs to a group of chemicals called cannabinoids. THC is also a cannabinoid chemical. THC mimics the actions of anandamide, meaning that THC binds with cannabinoid receptors and activates neurons, which causes adverse effects on the mind and body.
After you inhale marijuana smoke, its chemicals are distributed throughout the body.
High concentrations of cannabinoid receptors exist in the hippocampus, cerebellum and basal ganglia. The hippocampus is located within the temporal lobe and is important for short-term memory. When the THC binds with the cannabinoid receptors inside the hippocampus, it interferes with the recollection of recent events. THC also affects coordination, which is controlled by the cerebellum. The basal ganglia controls unconscious muscle movements, which is another reason why motor coordination is impaired when under the influence of marijuana.