Strong marijuana can increase the risk of addiction and psychosis, study suggests. Here are the symptoms to look out for.

• Strong cannabis may increase a person's risk of developing psychosis or addiction, an analysis has found.
• Cannabis is the most commonly taken drug globally, according to the UN.

High-strength cannabis appears to be more addictive and more likely to trigger psychosis than less potent forms of the drug, research suggests.

In the US and Europe, the concentration of the psychoactive ingredient THC in cannabis, which determines the potency of the drug, has more than doubled in the past 10 years, the authors of an analysis published on Monday in The Lancet Psychiatry said, citing a previous study.

Researchers examined 20 studies involving almost 200,000 users and suggest that people who use high potency cannabis may be more likely to experience addiction and psychosis than those using low potency products. Psychosis is when thoughts are so disturbed that people lose touch with reality.

One of the most rigorous studies found high-potency cannabis, compared to low-potency cannabis, may be linked to a four-fold increased risk of addiction, study co-author Tom Freeman, director of the Addiction and Mental Health Group at the University of Bath, UK, told CNN.

Cannabis is the most widely used drug globally, according to a 2021 United Nations report. In the US, state laws determine if people can use the drug legally. According to the CDC, cannabis is the most commonly used federally illegal drug in the US.

Kat Petrilli, a PhD student at the University of Bath, who co-authored the study, told Insider that it wasn't possible to define high and low potency in the review because it varied among studies. The authors were only able to compare the effects of higher potency cannabis with lower potency cannabis.

Five milligrams is the standard potency used in trials, but it can vary.

Freeman said in a statement that the findings suggest people who use cannabis could reduce their risk of harm by using lower potency products.

Petrilli told Insider that in places where it's legal, the concentration of THC might be specified on a product's packaging, while in illegal markets it may not be possible to tell how strong cannabis is.

Cravings and withdrawal are signs of cannabis addiction

According to the CDC, three in 10 people that use the drug have a cannabis addiction, also known as cannabis use disorder, or marijuana use disorder.

Signs of cannabis use disorder can include:

• Cannabis cravings
• Being unable to quit or control the amount used
• Spending a lot of time using the drug
• Disengagement with work, school, or social activities
• Needing more cannabis for the same effects
• Ignoring any social or relationship problems caused by its use
• Using the drug in high-risk situations, such as driving
• Withdrawal when attempt to stop use

Cannabis psychosis can cause paranoia and hallucinations

According to the CDC, people who use cannabis are at risk of both temporary psychosis and long-lasting mental health conditions such as schizophrenia.

Symptoms of temporary psychosis include: not knowing what is real, hallucinations, and paranoia.

Cannabis research is still in its infancy

The researchers cautioned in the review that the 20 studies included in the analysis mostly relied on participants reporting how potent the cannabis they used was, which could be unreliable. They also said it wasn't clear from research so far whether or not people who use high-potency weed were also at higher risk of anxiety or depression.

Ziva Cooper, the director of the UCLA Center for Cannabis and Cannabinoids, who was not involved in the research, told NBC that the field of cannabis research was still "in its infancy." The study left many questions to be answered, she said.