Drinking when you’re sad or anxious is not an unfamiliar scenario. Many Bollywood movies and songs have shown us that alcohol is associated with pain. Or how people smoke when they’re nervous because it’s the only thing that seems to calm them for a moment. If this is something you or someone you love might relate to, you’re far from alone. 

Mental illness and substance use disorders (SUDs) often co-occur. Nearly half the people who experience a mental illness at some point in their life also experience substance use disorder, and vice versa. This isn’t simply a coincidence or a simple one-cause-one-effect. Sometimes substance use may bring on mental health struggles, and sometimes mental health problems can lead to substance use. And often, they are both caused by some other common factor. 

In this blog, we talk about why this happens and what the best way is to treat co-occurring disorders. 

How common is this overlap?

As mentioned, close to half the people who deal with mental illness will also, at some point in their lifetime, deal with substance use disorders. This is also true for adolescents. In community-based substance use treatment programs, more than 60% meet the criteria for another mental illness (NIDA, 2020). This reflects that this is something that may take root long before adulthood. 

These are significant numbers and not anomalies. This also shows that this is something rooted in biology rather than a personal weakness or moral failure. 

Using substances to cope with emotional struggles

One of the most common reasons for mental illnesses and substance use to overlap is something psychologists call self-medication. This means using a substance to numb, escape, or manage difficult emotions or symptoms even briefly. Not for the fun or the high, but to feel okay. 

This can show up differently in different people. Someone might have a drink to deal with their social anxiety before a social gathering. Someone who might have difficulty sleeping due to anxiety might use cannabis to calm down or to focus. Someone struggling with symptoms of depression may use a stimulant just to get through the day. Sometimes, people may use substances to cope with the side effects of psychiatric medication. 

It creates a cycle that is difficult to get out of because the substances seem to work, at least for a short while. But in the long term, the substances make the same symptoms that they helped manage worse. Both immediately and over time. 

Nobody deliberately chooses to be stuck in this cycle. It is hence important to see that self-medication is an attempt to cope, not a character flaw. 

Common risk factors for mental health and substance use disorders

For an appropriate diagnosis, “which came first?” is an important question. But there may often not be a clear answer. This is because neither one may cause the other but instead grow out of some other common underlying roots. 

Genetics

Genetics play a bigger role than most people realize. An estimated 40–60% of a person’s vulnerability to substance use disorders comes down to genetic factors (NIDA, 2020). Many of the brain chemicals, like dopamine and serotonin, control mood, motivation, and reward. These are influenced by genes and are directly involved in addiction and mental illness. 

Neural systems

The same circuits that govern reward, decision-making, impulse control, and emotion are affected by addictive substances. These are the same circuits that get disrupted in conditions like depression and schizophrenia. Both substance use and mental health disorders are built on overlapping mechanisms. 

Trauma

Chronic stress and adverse experiences early in life raise the risk of both mental illness and substance use. People who’ve lived through trauma face a much higher risk of substance use and substance use disorders (NIDA, 2020). Traits like impulsivity, along with experiences of trauma, deprivation, homelessness, loss, or abandonment, can raise a person’s vulnerability to both psychosis and substance misuse. 

How does substance use impact mental health?

So far, we’ve looked at how mental health struggles can lead someone toward substance use but the relationship runs the other way too. Substance use can trigger or worsen symptoms of mental health disorders. Sometimes this may happen even in people who had no prior history of mental illness at all.

Substances can trigger the first episode of mental illness. In someone who is vulnerable, substance use can trigger symptoms of a mental illness that might never have surfaced otherwise, or bring back symptoms in someone with a past history (Nathan & Lewis, 2020).

Certain substances are more closely linked to certain effects. Cannabis, synthetic cannabinoids, stimulants, and hallucinogens are commonly associated with triggering psychotic experiences. About a third of people who experience a substance-induced psychotic episode go on to be diagnosed with a schizophrenia-spectrum or bipolar disorder later on. 

Its important to note that the “drug-induced” explanations can sometimes be oversimplified if not used cautiously. In reality, the relationship between substance use and mental illness is usually a mix of multiple, shifting, two-way influences over time. This is important because when we rush to blame the substance, we risk missing the fuller picture of what someone actually needs. 

What does treatment look like for dual diagnosis?

Since it is clear how intertwined mental illness and substance use is, it doesn’t make sense to treat them as separate, unrelated problems. Integrated care means treating both the mental health condition and substance use together. Research shows that integrated treatment for co-occurring substance use and mental illness has consistently outperformed treating each condition on its own.

In practice, integrated care can include:

• Behavioural therapies, such as cognitive behavioural therapy or motivational approaches, to help build coping skills for both conditions at once (NIMH, 2025)
• Medication, where appropriate, to support both mental health and substance use recovery
• Family-based support, which focuses on communication and relationships that can either support or strain recovery (NIMH, 2025)
• Practical, everyday support which includes help with housing, work, or other life stressors that keep the cycle going (NIDA, 2020) 

Each person and their condition is unique. So the treatment has to be tailor-made to address their unique diagnosis. 

Conclusion

The overlap between mental illness and substance use is the product of biology, environment, and coping, all tangled together in ways that even researchers are still working to fully understand. 

Understanding the mechanisms of this overlap can change how we respond to it. Replacing shame with compassion. Nobody wants to be stuck in this cycle. And everybody deserves the right support and treatment. 

If you’re looking for where to start, India now has several rehabilitation centres that specialise in exactly this kind of integrated, dual-diagnosis care.

• Sanctum Wellness and Healing in Delhi treats substance use and mental health conditions together, with individualised care plans and dedicated family therapy support. 
• Alpha Healing Center, located near Vadodara in Gujarat, offers evidence-based treatment for addiction alongside co-occurring mental health disorders, combining medical care, psychotherapy, and relapse prevention in one coordinated programme. 
• Lotus Wellness in Pollachi, near Coimbatore, similarly emphasises dual-diagnosis treatment, pairing psychiatric care with addiction therapy for conditions like depression, anxiety, bipolar disorder, and PTSD that often underlie substance use.

You can explore more rehab centers across India that specialise in dual diagnosis on our curated list here.