Models of Mental Disorder and Crime

The relationship between mental disorder and crime is complex and cannot be understood through a single lens.
Previous observations of the criminal justice system indicate an overrepresentation of persons with mental disorders (PMD).
There are a variety of reasons for this overrepresentation, necessitating structured models to understand how mental illness and criminal behavior intersect.

The Pathways Model, established by Hiday in $1997$ and updated in $2000$ , identifies three distinct routes to help understand the relationship between mental disorder and offending:
- Direct pathways.
- Indirect pathways.
- Common causal factors pathways.

A direct pathway occurs when a mental disorder, or the specific symptoms of that disorder, directly leads to or causes offending behavior.
Specific mental disorder symptoms that may directly elevate the risk of criminal activity include:
- Kleptomania.
- Disorders related to impulse control.
- Mania.
- Conduct disorders.
- Hallucinations.
- Delusions.
Evidence regarding the direct pathway provides the following insights:
- There is some association between major disorder symptoms and offending.
- Evidence for auditory command hallucinations as a direct cause is considered limited.
- Persecutory delusions and Threat/Control-Override (TCO) delusions are identified as risk factors, but the available evidence for these as direct causes remains limited.
Symptoms alone are insufficient to explain the broad relationship between mental disorder and offending.

In an indirect pathway, the mental disorder or its symptoms lead to other outcomes or variables, which then cause offending.
The mental disorder acts as a precursor to intermediary factors such as:
- Social deprivation.
- Substance abuse.

The common cause pathway involves variables that independently cause or lead to both a heightened risk for mental illness and a heightened risk for offending.
In this model, the relationship between the disorder and the crime is not necessarily causal in either direction; rather, they both stem from the same underlying factors.

Substance use is often considered the most important variable in the relationship between mental disorder and crime.
Key findings regarding substance use include:
- Individuals with a mental disorder and co-occurring substance use problems (comorbidity) are significantly more likely to offend than individuals who have a mental disorder alone.
- Substance abuse on its own is strongly associated with an increased risk of offending.
- A high proportion of persons with mental disorders (PMD) also suffer from a co-occurring substance abuse problem.
There are several reasons for high rates of substance use among PMD:
- Increased risk of substance use overall.
- Self-medication to manage the symptoms of their disorder.
- Increased sensitivity to the effects of substances compared to the general population.
- Substances can directly cause mental disorders.
- Substances can trigger mental disorders in individuals who are already biologically or psychologically predisposed to them.

Social stressors and environments play a significant role in both indirect and common cause pathways.
Key social risk factors include:
- Low socio-economic status.
- High levels of social stress.
- General social deprivation.
These factors create a cycle where social deprivation feeds into mental disorder symptoms or directly into offending, or acts as a common variable fueling both.

There is significant overlap between different types of mental health conditions:
- Approximately $16.5\%$ of individuals with a major mental disorder also have $1$ or more personality disorders.
- There is a significant overlap specifically between major mental disorders and Antisocial Personality Disorder (ASPD).

The way society perceives and responds to persons with mental disorders influences the likelihood of criminal justice involvement:
- PMDs are frequently perceived by the public and authorities as dangerous.
- PMDs may be more likely to experience social encounters that escalate and result in violent outcomes.
- The experience of victimization is a strong predictor of violence for persons with mental disorders.

The relationship between mental disorder and crime is multi-faceted and cannot be considered in isolation.
Other variables, such as substance abuse, personality disorders, social deprivation, and victimization, account for a significant portion of the relationship.
To effectively reduce offending among PMD, interventions must address co-occurring variables in addition to treating the primary mental disorder.
A schematic understanding must integrate mental illness, other conditions, and environmental factors to explain violence and crime effectively.