The brain continues to grow and develop from before birth into the mid-20s. During this time, it is vulnerable to the effects of addictive substances such as nicotine, alcohol, and marijuana. Using substances can cause serious changes in the brain affecting how a person thinks and acts. Those changes could last long after a person has stopped using substances and, in some cases, might be permanent.

Marijuana Use, Pregnancy & Risks to Fetal Brain Development

When a pregnant person smokes, vapes, or uses marijuana edibles, the chemicals can pass through the placenta to the baby. Babies exposed to marijuana during pregnancy can test positive for the drug after they are born. While more research is needed to know for sure, studies suggest that marijuana use during pregnancy could:

  • Cause a baby to be born too early leading to serious health problems at birth and throughout life.
  • Change how a baby’s brain develops which may cause lifelong behavior problems like
    • trouble paying attention
    • problems following rules
    • impulsiveness
    • depression and anxiety
  • Lower a child’s IQ
  • Cause problems with learning and memory making it harder to do well in school.

Marijuana Use, Breastfeeding & Risks to Infant Brain Development

Using marijuana while breastfeeding could also harm the baby, just like tobacco or alcohol. THC, the most common chemical in marijuana, can stay in human milk for up to six weeks. THC also builds up in the fat and blood of both mom and baby. Marijuana use during breastfeeding has been linked to:

  • Feeding problems
    • THC can lower milk supply
    • Babies may be less willing to eat which could lead to slow weight gain and growth
  • Some studies have shown that babies exposed to THC in breastmilk may have an increased risk for sudden unexpected infant death (SUID)

Although marijuana is a plant, that does not make it safe to use during pregnancy.

Marijuana Use & Risks to Adolescent/Young Adult Brain Development

From early adolescence through the mid-20s, the brain develops somewhat unevenly. The parts of the brain to develop first are those that control physical activity, emotion, and motivation. The prefrontal cortex, which is responsible for impulse control, more reasoned thought, and good judgement, develops later.

Developing brains are more susceptible than an adult brain to damage from outside influences such as nicotine, alcohol, and marijuana. This means substance use during the teen years creates a more distinct risk for immediate and lasting harm.

A lot of changes are taking place as the brain develops. New connections are forming between nerve cells, while other existing connections are getting stronger. Connections the brain no longer needs are pruned. These connections determine how the brain processes information. THC can negatively impact brain chemistry.

The endocannabinoid system plays a crucial role in brain development and helps control anxiety, memory, and motivation. THC can disrupt the chemical signaling and leave an imprint on the brain’s structure. These structural changes and disruptions to the normal brain development of teens and young adults could contribute to more significant and long-lasting changes such as:

  • Poor judgement
  • Impaired abstract thinking
  • Impulsiveness
  • Poor memory
  • Lack of motivation
  • Trouble managing emotions
  • Poor sleep quality
  • Increased risk for addiction (cannabis use disorder)

In addition, regularly using marijuana with a high THC content may increase the risk of mental health problems like schizophrenia psychosis and thoughts of suicide.

Delaying marijuana use until after the age of 25 can lower the risk of developing harmful health effects in the future.