Dual Diagnosis (Co-Occurring Disorders)
First identified in the 1980s, the term dual diagnosis refers to the simultaneous presence of a serious mental illness and a substance abuse disorder.
The Substance Abuse and Mental Health Services Administration recognises this as co-occurring disorders, a condition where an individual battles both substance-related issues and mental health problems.
What is Dual Diagnosis?
Dual diagnosis is a term applied when an individual is grappling with one or more mental health conditions – such as anxiety, personality disorders, or depression – along with a substance use disorder, which might include dependencies like alcoholism or opioid abuse. Another term for this is comorbidity.
For example, a person might be dealing with an addiction to drugs, alcohol, or both, and simultaneously suffer from a psychiatric condition like schizophrenia, depression, or borderline personality disorder. Dual diagnosis treatments aim to address both issues paving the way for a comprehensive and sustainable recovery.
The severity of substance use and psychiatric disorders can vary significantly. Individuals with co-occurring disorders often require more intensive and prolonged treatment due to the complex nature of their physical and mental health challenges.

What Causes Co-Occurring Disorders?
Co-occurring disorders can be traced back to a blend of internal and external factors, including genetic and environmental influences.
Genetics
Research indicates the significant role of genetics in both addiction and mental health issues. Individuals with a family history of addiction or depression are more prone to similar challenges, with multiple contributing factors at play.
Recent scientific studies into addiction genetics have discovered distinct differences in the functioning of certain genes and gene networks in individuals with addiction compared to those without such a history. Additionally, prenatal exposure to substances or toxins is linked to an increased risk of mental health challenges later in life.
Environment
Environmental factors significantly contribute to the occurrence of co-occurring disorders. For instance, children raised in environments where drug and alcohol use is common may adopt these behaviours, perceiving them as normal.
Mental illnesses can also develop due to various environmental stressors such as life-altering events (e.g., divorce, the death of a loved one, financial strain), exposure to certain drugs or chemicals, and traumatic experiences like severe traffic accidents or physical or sexual abuse.
Other risk factors
- Family history of substance abuse or addiction
- Struggles with self-esteem or self-image
- Prenatal exposure to drugs, toxins, and viruses
- Family history of mental illness
- Gender factor, with a higher tendency for men
to seek treatment for dual diagnosis

Types of co-occurring disorders
- Mood Disorders
This broad category includes all forms of depression and bipolar disorders - Anxiety Disorders
Persistent, escalating anxiety over time can signal an anxiety disorder - Psychotic Disorders
These are marked by hallucinations and delusions - Eating Disorders
Serious mental health conditions that involve harmful eating behaviours - Personality Disorders
This group includes various disorders like schizoid, schizotypal, narcissistic, and histrionic personalities - Behavioural Disorders
Examples include attention deficit, hyperactivity, conduct, and oppositional disorders
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