Decoding Cannabis: Can cannabinoids help treat mental health conditions?

Mental illness has long been one of the most stubborn medical puzzles. Up until just a few short decades ago, our understanding of conditions like depression or schizophrenia was patchy at best - a mix of symptom lists, educated guesses, and trial-and-error prescriptions. 

Even now, many of the conventional treatment options patients rely on were discovered accidentally, and their success often hinges as much on luck as biology.

But as neuroscience has evolved, so too has our view of the brain. 

In this Decoding Cannabis blog series continuation (where we dig into one recent study at a time to make sense of the science), we turn our attention to cannabis for mental health conditions.

“Cannabinoids and their therapeutic applications in mental disorders” a 2020 clinical review, is the study in question today. It is one of the most comprehensive reviews of the currently available data. 

The paper brings together findings from dozens of human and preclinical studies to evaluate whether cannabinoids (both plant-based and synthetic) might offer new therapeutic pathways for patients with depression, bipolar disorder, anxiety, PTSD, and schizophrenia.

The results are intriguing, but they are also cautious. While the authors stress that more high-quality clinical trials are needed, especially in patients with formally diagnosed psychiatric illnesses, the currently available rationale for cannabinoid-based treatments is compelling - and in some cases, the early clinical data is even more so.

The problem with current mental health treatments

Mental health conditions are staggeringly common, affecting as many as 1 in 4 people worldwide. But we still don't have a complete understanding of the mechanisms behind them, or why some people respond well to conventional treatment options, while the opposite is true for others.

Patients with depression, anxiety, OCD, PTSD and schizophrenia often don’t respond predictably, or well, to pharmaceutical options. And when they do, the benefits may be partial, delayed, or come at the cost of difficult and heavy side effects.

Standard prescriptions like SSRIs, benzodiazepines, and antipsychotics can certainly be life-changing for some. But for an estimated 30 to 60% of patients, standard treatments don’t go far enough, with many experiencing only partial relief, if any at all. Current estimates suggest that nearly one-third of patients with major depression meet criteria for treatment resistance, and broader reviews suggest even higher rates across other disorders.

Why don’t antidepressants work for everyone?

Selective serotonin reuptake inhibitors (SSRIs) and benzodiazepines have long been the go-to prescribable options for depression and anxiety. But these drugs were developed decades ago, based on a now (at least slightly) outdated understanding of brain chemistry - with newer research showing that “the cause of depression has been oversimplified and drugs designed to treat it aim at the wrong target”. 

While they are affective for some, they usually take a few weeks to show results. But many don’t get these results, and instead encounter emotional blunting, weight gain, sexual dysfunction, or worse.

Could cannabis help when standard treatments fail?

That’s the question researchers are beginning to take seriously, and what we are here to dissect.

The last two decades or so has seen a growing interest and understanding in the endocannabinoid system (especially in its role in regulating emotional responses, memory, and stress). 

The cannabinoids (THC and CBD primarily) offered up by cannabis and hemp plants are now being researched as complementary, or even alternative treatment options for many of the more commonly seen mental health concerns of today. 

Evidence for cannabinoids in mental health: what the study shows

Depression: promising biological targets, limited clinical trials

For many people living with heavy bouts of depression, symptomatic relief can be hard to find through conventional treatment routes. This has pushed researchers to turn their attention to the body’s own internal chemical balance, and in particular, the endocannabinoid system.

Does depression affect your natural cannabinoid levels?

People with depression tend to show lower levels of natural cannabinoids like anandamide and 2-AG. Some postmortem studies suggest that the brain might try to compensate by increasing the density of CB1 receptors, particularly in areas linked to mood regulation. It’s a clue, not a full and clear answer, but one that’s drawn interest toward cannabis-based therapies.

Can CBD or THC relieve depressive symptoms?

CBD, in particular, has shown early promise in mood-related studies. Observational data suggest it may ease symptoms for some, especially those self-medicating with low-THC or balanced strains. But the hard evidence is still thin. 

There are no high-quality clinical trials yet, and some findings suggest long-term/unregulated (non-prescribed) cannabis use - especially with high-THC products, could make things worse.

That’s not to say patients with depression need to avoid THC entirely, only that its administration must be overseen and monitored by a specialist clinician, with careful attention to dose, ratio, and individual response.

CBD, THC and anxiety: what the science is telling us

Anxiety is also one of the most common reasons patients in the UK are prescribed medical cannabis. While CBD has drawn the lion’s share of research attention, there’s a growing body of evidence suggesting both CBD and THC may have a role to play, depending on the patient’s needs, the dose, and what type of anxiety is being treated. 

Can CBD reduce anxiety without causing side effects?

In trials, moderate doses of CBD (typically 300 to 600 mg) have been shown to reduce anxiety, particularly in social settings or acute stress scenarios. Brain imaging supports this too: CBD seems to quieten the amygdala, one of the brain’s key fear-processing hubs. It also does so without the drowsiness, dependency, or cognitive repression that can come with conventional antianxiety medications.

What does the research say about cannabis and panic?

According to this paper, while high doses of THC can ramp up anxiety (particularly in people new to cannabis, or in unpredictable recreational settings) that doesn’t mean all THC is off-limits. The study outlines the risks of THC in anxiety, but also notes that many participants found relief from low-potency THC treatment options, particularly when taken alongside CBD. 

The right dose of THC, in the right patient, at the right time (with clinical oversight and ongoing monitoring), can be calming rather than chaotic.

PTSD: a role for cannabinoids in trauma recovery?

Post-traumatic stress disorder isn’t just a matter of nightmares and flashbacks. It can leave a structural imprint on the brain, reshaping how we process fear, safety, and emotional threat. For many people with PSTD, it becomes a constant low hum of over-vigilance, heavy restlessness, and emotional volatility that conventional treatments struggle to help control.

How does the endocannabinoid system affect trauma recovery?

There are signs that cannabis for PTSD symptom control may offer a new direction. 

People with PTSD often show lower levels of anandamide (AEA), one of the human body’s own cannabinoids. Some also display increased CB1 receptor activity, possibly the brain’s way of trying to compensate for this lack of the human-produced cannabinoid that binds strongly to this receptor type. This imbalance hints at why plant-based cannabinoids might help restore emotional regulation.

Can THC or CBD reduce PTSD-related nightmares?

THC, particularly in low doses, has shown promise in reducing nightmares and improving sleep. CBD, too, appears to calm hyperarousal and reduce intrusive symptoms, without the intoxication.

Still, the evidence is early and the results mixed, at least from a clinical standpoint. 

While several promising trials are underway, cannabinoid-based treatments for PTSD are best approached with care, clinical oversight, and a personalised treatment plan that accounts for individual needs and responses.

Bipolar disorder: high use, unclear benefit

According to the study, unsupervised, non-prescribed cannabis use is common among people living with bipolar disorder. 

Bipolar sufferers reported turning to it in search of relief from disruptive mood swings, sleepless nights, or the heavy side effects of conventional medications. Some say it helps. 

But the clinical picture is far from clear.

Why do people with bipolar disorder use cannabis?

Anecdotally, non-prescribed cannabis is taken to ease symptoms like low mood, racing thoughts, or insomnia. Some report feeling more stable or focused. And while personal experience shouldn’t be dismissed, self-reported benefits don't always translate into clear medical efficacy - especially when it comes to a condition as complex as bipolar disorder.

Does CBD help manage bipolar symptoms?

So far, trials investigating CBD for mood stabilisation have been limited in both scale and outcome. 

Results suggest it may offer relief for related issues like sleep or anxiety, but doesn’t appear to have a clear effect on core manic symptoms. THC, on the other hand, may pose more risk than benefit. Evidence indicates that cannabis use may worsen manic episodes in some individuals - particularly when used unsupervised or in high doses.

At Releaf, we approach this with caution. 

While there is growing evidence that cannabis and bipolar disorder often intersect in bipolar patient collected data, we recognise the lack of conclusive proof that cannabis-based medicines are safe or effective for this diagnosis. 

At Releaf, we generally do not prescribe cannabis-based treatments to patients who have been diagnosed with certain complex mental health conditions, and this includes bipolar disorder. This is because there is inconclusive evidence to support the use of medical cannabis in bipolar disorder treatment plans, and there are significant risks associated with the use of cannabis in individuals who have bipolar disorder. As healthcare providers, it’s imperative we act responsibly and put patient safety first.

While Releaf always takes the most cautious approach, we’re open to case-by-case review - particularly where individuals have been stable for extended periods and have clear support from their GP or mental health team. 

But this remains the exception, not the rule.

Schizophrenia and psychosis: why CBD shows promise, but treatment isn’t advised

Medical cannabis is not an appropriate treatment for schizophrenia or other psychotic disorders. In the UK, patients with a history of psychosis or a diagnosis of schizophrenia are disqualified from medical cannabis treatment. The risk profile is simply too high.

Still, researchers have spent years trying to understand the role of the endocannabinoid system in psychosis. 

Schizophrenic patients often show elevated levels of anandamide (AEA), one of the body’s two natural cannabinoids, and some studies suggest this might act as a protective mechanism trying to offset the brain’s deregulated signals. CB1 receptor changes have also been found in relevant brain regions, though the data is inconsistent and often contradicts itself.

Can CBD reduce hallucinations or delusions?

CBD has drawn cautious interest. 

Unlike THC, it does not appear to worsen psychosis (and some early-stage trials suggest it may even reduce symptom severity when used alongside antipsychotic medication). A few studies have shown that CBD may improve cognitive performance and ease hallucinations or delusions, potentially by increasing endocannabinoid expression through AEA preservation - although this finding has not been fully confirmed in the study. 

It is also important to point out that these studies were small in participancy, short in duration, and far from conclusive.

And while some patients showed improvements, others saw no benefit at all. With the current body of clinical evidence being as shaky as it is, and with the issues surrounding THC administration, it would be irresponsible to treat CBD as a relevant and safe option in psychotic disorders until further clinical trails have been completed. 

Why is THC risky for people with schizophrenia?

THC is a well documented risk factor for people with schizophrenia. Heavy/frequent use (particularly with high-potency cultivars - above 25% THC) has been repeatedly linked with earlier onset, worsened symptoms, and greater psychosis relapse risk. 

Even in the general population, early THC exposure is associated with an increased likelihood of psychosis in vulnerable individuals. So while the biological pathways that CBD may help with are very interesting and worthy of further study, cannabis-based treatments are not suitable for this group. 

At Releaf, we do not prescribe cannabis to patients with schizophrenia or a history of psychotic illness. The current evidence does not support it, and in cases like these, safety must come before speculation.

Where do we go from here?

The “Cannabinoids and their therapeutic applications in mental disorders” study (along with the growing list of emerging research papers) gives us an extremely fascinating snapshot of where things currently stand, but also where they don’t. 

While some findings are encouraging, especially for medical cannabis for anxiety, depression, and PTSD management. The evidence is far from complete. Larger, better-controlled random control trials are the necessary next step (and they’re currently underway, with more planned for the coming years). 

At this point, medical cannabis treatment is more suited to being a complementary add-on rather than an alternative for conventional options. Mental health is complex, and single-molecule pharmaceuticals rarely help reduce the overall symptomatic toll. Hopefully, in the coming years, we’ll have a clearer picture of where cannabinoid-based treat fits for a much larger list of mental health issues. 

For now, we can say that medical cannabis offers a natural, supportive role for some patients, under careful specialist driven clinical guidance. This means measured doses, clinician oversight, and a personalised approach that accounts for both risk and response.

If you’re struggling with a mental health condition and are interested in learning more about whether medical cannabis might be appropriate, Releaf offers evidence-informed guidance and specialist support. Every treatment plan is built around you - not just the symptoms. 

Head to our medical cannabis eligibility checker to find out if treatment could be an option for you, and take the first step towards personalised, clinically-guided medical cannabis care.