What is a dual diagnosis?

This is the part that catches a lot of people off guard, because from the outside it can look like two separate problems. In reality, they’re usually tangled together in ways that make each one harder to manage on its own.

When mental health drives the substance use

One of the most recognised patterns behind a dual diagnosis is something researchers call self-medication. This is where someone starts using a substance to manage the symptoms of a mental health condition.

Signs of someone self-medicating could include:

• Abusing alcohol to deal with depressive episodes
• Misusing stimulants to cope with depressive episode
• Relying on sleeping pills just to get a few hours of sleep

The problem here is that while this method can provide relief, it’s always temporary and once the effects wear off it can make the original symptoms even worse than they originally were.

For example, alcohol is a depressant, so while it might help with low mood for a few hours, it can make things worse once it leaves the system.

Stimulants like cocaine produce come-downs which can exacerbate existing depression or anxiety symptoms.

When substance use creates new mental health issues

The cycle works in the other direction too. Chronic substance use can disrupt the brain’s mood-regulating systems and trigger psychiatric symptoms that weren’t there before.

One review found that 40-60% of people with alcohol use disorder experienced depressive episodes directly linked to their drinking.

Cannabis abuse during adolescence has also been consistently linked to higher rates of psychosis in adulthood.

So the question of “which came first” doesn’t always have a clean answer and in many cases both conditions end up reinforcing each other until they’re very difficult to pull apart.

Recognising a dual diagnosis is not always straightforward, especially when both conditions have been present for a long time. But there are patterns that can help you work out whether what you’re experiencing or what you’re seeing in someone else, goes beyond a single issue.

For yourself

One of the clearest indicators is noticing that your mental health symptoms get worse during or after substance use.

If low mood deepens in the days following drinking or if anxiety spikes become more frequent alongside stimulant use, that connection is worth paying attention to.

Another sign is using substances specifically to manage how you feel rather than for social reasons, like drinking before bed because sleep feels impossible without it.

When a substance becomes tied to how you regulate your emotions, it suggests something deeper is driving the use.