Can weed turn a bubbly, ambitious 30-year-old into a sluggish, apathetic 50-year-old?
We’re going to dive into the effects of weed on the brain and body, covering short-term and long-term effects, before answering the question: “does weed change personality?”
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Weed is an psychoactive drug that can be smoked (as a spliff or bong), vaped, or taken as an edible. In the UK, it’s an illegal substance.
You may hear many other names for weed, including:
Though “weed” is often used as an alternative for cannabis, it technically refers to cannabis that is made by drying out the flowering parts and leaves of the plant, which gives the appearance of dried herbs.
The psychoactive element of cannabis comes from the THC. There is also a related ingredient, known as CBD, that isn’t psychoactive, and therefore doesn’t produce a “high” like THC does.
The effects of weed are unpredictable.
Generally, weed makes people feel more calm, relaxed, and detached for up to a few hours. It’s also common to experience the opposite effects; to feel more lively and talkative.
For many people, using weed leads to uncomfortable side effects, such as increased anxiety, and in some cases, paranoia.
These symptoms are more common in people who have pre-existing mental health conditions, those who use cannabis containing high levels of THC, and people who engage in frequent and/or heavy marijuana use.
However, with any weed use, there is a risk of negative short-term and long-term effects, including cannabis dependency or cannabis addiction.
The DSM-5 lists cannabis use disorder as a type of substance use disorder.
Cannabis use disorder is more than just consuming cannabis from time to time.
It’s a full-blown addiction, that fits in with the 11 criteria of substance use disorders, including hazardous use and cravings.
People with this disorder can transition into recovery, but it usually takes medical intervention, such as cannabis rehab.
In the year ending March 2023, around 2.5 million people living in the UK reported using cannabis (1).
Weed remains the most common substance that young people seek treatment for, making up 87% of cases (2).
Though people of all ages are affected by this addiction, young people are three and a half times more likely to develop severe cannabis use disorder (3).
Before we answer “does weed change personality?”, we need to define what we mean by “personality”.
Personality is “the type of person you are, shown by the way you behave, feel, and think” (4).
More specifically, let’s look at the Big Five personality test (the most widely accepted theory in personality psychology) (5). It uses five dimensions to describe personality, which are:
Our personality can subtly evolve over time. Different life events can cause changes in personality, and changes can also occur due to intentional self-improvement,, e.g., trying to worry less.
However, it’s rare for someone’s personality to become dramatically different, as elements of personality are believed to be innate.
When someone uses weed and thinks, feels or behaves very differently, it isn’t usually a personality change we’re looking at, but a mood change.
Shifts in mood are very common with cannabis use, but they are temporary, so the effects wear off within a few hours.
People tend to act differently when they’re “stoned”. Let’s explore the science behind this.
Cannabinoid receptors help with communication between our brain cells. They work as part of a well-oiled machine, following an organised structure with precise timing and balance.
When someone uses cannabis, THC activates these receptors, but in a less controlled way than the brain’s natural chemicals. The result can be a temporary alteration in normal brain communication.
From the outside, this looks like shifts in thoughts, feelings, and behaviours. Some people experience:
When we look at the Big Five personality traits, we can see that personality can be temporarily impacted by cannabis. Users may feel:
However, the likelihood is that the person’s natural personality traits will return to normal post-weed. Highly agreeable individuals are very unlikely to become permanently apathetic after using cannabis.
Is the “lazy stoner” stereotype really true? Does weed cause people to become lazy, lethargic, and apathetic?
“Amotivational syndrome” would suggest there is some truth to the stereotype.
This condition, linked to habitual substance use, is characterised by low motivation and ambition, and has been strongly linked to weed in particular.
Studies of this syndrome suggest a link between cannabis users and high levels of apathy (6).
However, there is no conclusive evidence to prove that cannabis users are suffering from amotivational syndrome.
Too many other factors are at play, such as mental health conditions and the environment the individual is in.
People who are already struggling with motivation may be more likely to turn to cannabis, which skews results.
There is a significant difference in risk between someone who occasionally uses weed, and someone who is a chronic user.
Many adults, particularly in the former category, do not experience overt personality shifts after many years of using weed.
Their openness, conscientiousness, extraversion, agreeableness and neuroticism tend to stay reasonably predictable throughout their life.
That being said, they are likely to experience mood shifts every time they use cannabis, and this can cause negative habits to form.
Over time, it is possible that this will have a permanent effect on their personality.
For example, if someone is regularly consuming cannabis, dopamine is being released frequently.
Over time, this can affect the brain’s ability to naturally produce dopamine, which has a negative effect on the reward system.
Chronic cannabis users can lose motivation and pleasure, as they are reliant on the “high” of weed to feel these things.
Recent research has discovered that our brain stays in the “adolescent” phase until our early thirties (7).
Before then, our brain is often still developing, making us more susceptible to damage from weed use. This can affect our energy levels, motivation, reaction times, coordination, memory, and judgement, amongst other key functions.
If someone uses cannabis regularly as a young adult, there is a risk that these functions can be impaired permanently.
Some weed users feel that weed brings them as close as possible to their authentic self. They may feel more creative, confident, and emotionally open.
It’s tricky to determine whether weed really does help people be true to themselves.
On one hand, certain effects can lower people’s inhibitions, allowing them to say and do things they wouldn’t normally feel comfortable with.
Is this authenticity? We can’t say for sure.
It appears that there’s a link between personality type and reactions to weed, i.e., if you’re already an anxious person, you’re more likely to experience cannabis-induced anxiety. In this sense, perhaps weed amplifies certain traits.
Yet, it’s never fully predictable. Someone could experience moods they rarely feel naturally, such as an emotionally stable person feeling depressed when they use weed. Who’s to say this temporary depressed state is that person’s “true self”?
Weed doesn’t automatically cause mental health disorders to develop. However, that doesn’t mean that there is no link between the two.
For some users, cannabis use can increase the risk of mental health issues, or exacerbate existing symptoms.
Whilst no one is immune from this, it’s more likely to occur in individuals who engage in heavy, frequent weed use, people who already struggle with their mental health, or young people with developing brains.
Weed users are at an increased risk of developing psychosis and schizophrenia.
Again, this is generally found in people with particular vulnerabilities (such as using high-THC weed frequently).
If the individual stops using the drug, their risk decreases (8).
There is no proven, solid relationship between weed and depression, anxiety, and PTSD.
However, there are indications that weed use can increase the risk of these conditions developing, or worsen existing symptoms.
For example, daily cannabis use is associated with a higher risk of social anxiety disorder (9).
Paranoia is not a mental health condition, but a symptom of various conditions.
A 2025 study found higher levels of paranoia in individuals who used cannabis to self-medicate, compared to those who used it recreationally (10).
Signs that cannabis may be affecting your personality long-term include:
We’ve learnt that weed can cause long-term personality changes, and can occasionally transform personalities permanently.
Each person’s reaction to weed is highly personal, and it can change with further use. Instead of focusing on whether weed changes personality in general, consider how weed interacts with your specific personality.
Explore how it makes you feel, which side effects you’re experiencing, and whether it’s affecting your thoughts, feelings and behaviours negatively.
We refer people with weed dependence or weed addiction to specialist treatment centres in their area (or beyond!)
You may feel capable of giving up weed whenever you want to, but the problem with dependence is that it sneaks up on you.
Always be mindful of the way you feel when you use weed, and look out for signs of dependence or addiction.
Our helpline is always open for you, whether you’re seeking immediate support or you’d like to know more about cannabis addiction.
Call 0800 140 4690 (UK) or +44 345 222 3508 (international) for more guidance. We’re here for you.
To conclude this discussion, we provide some FAQs around this topic:
Yes, cannabis with high levels of THC comes with more risk to your physical and mental health.
What’s more, there’s always a risk of cannabis being laced with other substances, from glass to heroin, which can be incredibly dangerous for the user.
Using cannabis and alcohol together can be dangerous, as alcohol often increases the effects of the weed.
There isn’t a consensus regarding whether cannabis causes withdrawal symptoms. However, many users report feeling a range of uncomfortable symptoms, from stomach pain to anger.
If you’re ready to give up weed, the safest option is to seek professional help. This can help you avoid dangerous withdrawal symptoms, and ensure you’re supervised in case your health deteriorates.
No, cannabis is not safe during pregnancy or breastfeeding. Regardless of the amount of weed, and the trimester the woman is in, no amount of weed is safe for the woman or unborn child.
Yes, regular cannabis use has been linked to impaired sleep.
Research suggests that increased edible consumption is linked to lower sleep duration and worse subjective sleep efficiency (11).
The best time is now. Addiction can spiral out of control very quickly, so it’s always best to seek professional support as early as possible.
If you’re still uncertain, and you’d like to know your options before proceeding, get in touch with Rehab 4 Addiction on 0800 140 4690 (UK) or +44 345 222 3508 (international).
Perhaps you know you need to make a change, and you’re prepared to take the first step today. Give us a call, and we’d love to tell you more about what we can do for you.
[4] https://dictionary.cambridge.org/dictionary/english/personality
[5] https://www.truity.com/test/big-five-personality-test
[6] https://pubmed.ncbi.nlm.nih.gov/32100610/
[8] https://www.kcl.ac.uk/news/psychotic-disorder-cannabis-use-cessation
[11] https://pmc.ncbi.nlm.nih.gov/articles/PMC7572650/
Boris is our editor-in-chief at Rehab 4 Addiction. Boris is an addiction expert with more than 20 years in the field. His expertise covers a broad of topics relating to addiction, rehab and recovery. Boris is an addiction therapist and assists in the alcohol detox and rehab process. Boris has been featured on a variety of websites, including the BBC, Verywell Mind and Healthline. You can connect with Boris online at LinkedIn or X.com.
