Marijuana Dependence: Symptoms and Signs


Marijuana (cannabis, weed, pot, reefer, grass, dope, Mary Jane) comes from the Indian hemp plant and is a mixture of dried leaves, stems, flowers and seeds. Although there are more than 400 chemicals in marijuana, the key chemical responsible for the “high” is tetrahydrocannabinol (THC), which is why it is classified as an illicit drug.1 The marijuana sold today has a very high THC content with very little cannabidiol, the compound often associated with medicinal benefits. Whether smoked, vaped, ingested as an edible or made into dabs (marijuana or hash extracted from the plant and concentrated into a smokable oil), marijuana can be especially harmful to adolescents whose brains are not fully developed.2

In the U.S., marijuana (cannabis) is widely available, which may explain why it is the most commonly used illicit drug. In 2014, an estimated 22.2 million people aged 12 and older reported using marijuana during the last month. Marijuana use can lead to the development of marijuana use disorder, which in severe cases turns into addiction. Recent data suggest that 30% or 4.2 million marijuana users met the criteria for cannabis use disorder based on marijuana use.3

Past data have suggested a link between marijuana use disorder and other substance use disorders (SUDs), as well as mood disorders such as depression, and anxiety disorders. Researchers could not prove whether the link was causal or attributed to common contributing factors. A study of nearly 35,000 participants found marijuana use was associated with a wide range of psychiatric disorders, although after adjusting for common underlying factors that predict marijuana use, the only co-occurring disorders that remained significant were other SUDs (e.g. alcohol and nicotine).4

Stats and Facts

  • A study published in 2016 of more than 47,000 adults aged 50 and older between 2006 and 2013 indicated marijuana use increased by 71% during that time period.5
  • A 2014 study of 127 teens (ages 14 to 19) treated at an outpatient substance abuse clinic indicated 90 were marijuana users. Of those, 84% met the criteria for marijuana dependence, including increased tolerance and unsuccessful attempts to reduce or stop using the drug.6
  • In 2015, 11.8% of youths in 8th grade reported marijuana use in the last year and 6.5% were current users. Among those in 10th grade, 25.4% used marijuana in the last year and 14.8% were current users. By 12th grade, 34.9% used marijuana during the prior year and 21.3% were current users, while 6% stated using it on a near daily basis.7

Marijuana Symptoms and Signs

Many adults do not exhibit signs of marijuana use, especially if they are occasional users. Parents should look for classic red flags if they suspect their teens are smoking marijuana, including:

  • Acting inappropriately giddy (e.g. laughing uncontrollably)
  • Eating ravenously
  • Newfound interest in baking brownies
  • Chronic bloodshot eyes and/or bad breath
  • Excessive use of breath mints, chewing gum and eye drops
  • Slacking off on responsibilities
  • Lethargy or listlessness
  • Poor attention span
  • Appearing stoned
  • Sudden drop in academic performance
  • Signs of depression or isolation
  • Abrupt change in friends
  • A sudden need for more money
  • Presence of small burns on the thumb and forefinger
  • Heavy use of incense in the bedroom
  • Drug paraphernalia in bedroom, backpack or purse (e.g. rolling papers, pipes, roach clips and bongs).8,9

Marijuana and the Brain

Until a person is in their early to mid-20s, the brain is thought to be particularly sensitive to damage from drug exposure. The frontal lobe — the region critical to planning, judgment, decision-making and personality — is one of the last areas to fully develop. Moreover, the endocannabinoid system that reacts to THC is immature in teenagers. This system is important for cognition, neurodevelopment, stress response and emotional control and helps modulate other major neurotransmitter systems. One study found people who started smoking before age 16 made twice as many mistakes on tests of executive function as those who started after age 16. This included planning, flexibility, abstract thinking and inhibition of inappropriate responses.10

Changes in the shape, volume and gray matter density of the nucleus accumbens (which plays a role in motivation, pleasure and reward processing) and the amygdala (a region involved in memory, emotion and decision-making) have been noted in marijuana smokers. These changes are most significant in heavy users.10

Marijuana and Mental Health

People addicted to marijuana are at a higher risk for experiencing the negative consequences of using the drug, such as short-term memory impairment and mental health problems. The association between marijuana use and co-occurring mental health disorders such as depression appears to differ based on the age people start smoking and the degree of use.11

A 2012 study found that people who smoked marijuana before age 17 were 3.5 times more likely to attempt suicide than those who started smoking marijuana later in life. This research also indicated people who were dependent on marijuana had a higher risk of experiencing major depression and suicidal thoughts and behaviors.11 Subsequent research published in 2014 indicated daily adolescent users were 18 times more likely to become dependent on marijuana, seven times more likely to attempt suicide and eight times more likely to use other illegal drugs in the future.12

A large-scale study found marijuana use as an adult is not associated with mood and anxiety disorders, including depression and bipolar disorder, contradicting the results of prior studies. However, the study confirmed previous findings linking marijuana use to an increased risk of developing SUDs later on, including addictions to alcohol, nicotine and other drugs.13

If you or a loved one is suffering from marijuana dependence, help is just a phone call away.

  1. What Is Marijuana? Drug Free World website. Accessed December 8, 2016.
  2. Who We Are. Moms Strong website. Accessed December 8, 2016.
  3. Substance Use Disorders. Substance Abuse and Mental Health Services Administration website. Updated October 27, 2015. Accessed December 8, 2016.
  4. Marijuana Use Raises SUD Risk. National Institute on Drug Abuse website. Updated February 2016. Accessed December 8, 2016.
  5. Baby Boomers Going to Pot. HeathDay website. Published December 6, 2016. Accessed December 8, 2016.
  6. ‘Pot Addiction’ May Be Real, Study Suggests. HealthDay website.  Published September 2, 2014. Accessed December 8, 2016.
  7. What is the scope of marijuana use in the United States? National Institute on Drug Abuse website. Updated August 2016. Accessed December 8, 2016.
  8. Commonly Abused Drugs Charts. National Institute on Drug Abuse website. Updated January 2016. Accessed December 8, 2016.
  9. Signs of Pot Use in Teens, From Breath Mints to Burns. Elements Behavioral Health website. Accessed December 8, 2016.
  10. Marijuana and the developing brain. American Psychological Association website. Published November 2015. Accessed December 8, 2016.
  11. Lynskey MT, Agrawal A, Henders A, Nelson EC, Madden PAF, Martin NG. An Australian Twin Study of Cannabis and Other Illicit Drug Use and Misuse, and Other Psychopathology. Twin Res Hum Genet. 2012;15(5):631-641. doi:10.1017/thg.2012.41.
  12. Frequent teen marijuana use linked to issues later in life. CNN website. Published September 10, 2014. Accessed December 8, 2016.
  13. Ingraham C. Study: Smoking pot doesn’t make you anxious or depressed. Washington Post. February 17, 2016. Accessed December 8, 2016.
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