An introduction and overview of the mental health conditions relevant to people with intellectual disability. The chapter focuses on the evidence base to support or refute whether they suffer greater rates of mental health problems, Psychiatric classification and prescribing; Comparison tables of international classification of diseases (ICD) versions 10 and 11; and the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM) 4 and 5 and DC-LD.

Personality refers to the innate and enduring characteristics that influence an individual’s attitudes, behaviours, and experience of themselves, others, and the world. Historically, personality disorders were conceptualised as enduring and pervasive disturbance in an individual’s patterns of thinking, feelings, and behaviours. This disturbance results in significant disturbance in their psychosocial functioning and interpersonal relationships The diagnosis of personality disorders in people with intellectual disability can be a contentious issue. The chapter presents an overview of the condition, the treatments with medication available, and their relevance.

Anxiety disorders are common mental health problems and include panic disorder, generalised anxiety disorder, post-traumatic stress disorder, and obsessive compulsive disorder. The chapter presents an overview of the condition, the treatments and medication available, and their relevance to people with intellectual disability.

Bipolar disorders are episodic mood disorders defined by the occurrence of manic, mixed, or hypomanic episodes or symptoms. Manic and hypomanic symptoms are characterised by a subjective experience of increased energy and activity, along with various other symptoms. These episodes typically alternate over the course of these disorders with depressive episodes or periods of depressive symptoms such as lowering of mood, decreased energy and activity (ICD-11, 2019; DSM-5, 2013). Both the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders DSM-5 and the International Classification of Diseases ICD-11 broadly subclassify the condition as follows: bipolar I disorder: one or more manic episodes or mixed episodes. Individuals often have one or more major depressive episodes; bipolar II disorder: one or more major depressive episodes accompanied by at least one hypomanic episode. Bipolar affective disorders present a major diagnostic and treatment challenge to services for people with intellectual disability. The chapter presents an overview of the condition, the treatments with medication available, and their relevance. The chapter includes the use of mood stabilisers such as sodium valproate.

According to the ICD-11 (World Health Organization, 2019), substance use disorders include disorders that result from a single occasion or repeated use of substances (both legal and illegal) that have psychoactive properties; all drugs that are taken in excess have in common direct activation of the brain reward system, which is involved in the reinforcement of behaviours and the production of memories. They produce such an intense activation of the reward system that normal activities may be neglected. Instead of achieving reward system activation through adaptive behaviours, drugs of abuse directly activate the reward pathways. The pharmacological mechanisms by which each class of drugs produces reward are different, but the drugs typically activate the system and produce feelings of pleasure, often referred to as a ‘high’ (American Psychiatric Association, 2013). This chapter will cover all substance use in people with intellectual disability, whether it is a problem, and alternative treatments.

This chapter provides an overview of clinical practice pertaining to offenders with intellectual disability. It covers the ‘offending journey’ of people with intellectual disability whose behaviour reaches the threshold for criminal justice system involvem’nt. This includes being accused of a crime, interactions with the police, decisions regarding prosecution and the processes involved in court cases. Though much of this account is based on the law in England and Wales, the chapter also reviews key research in this area, examining the risk factors for offending, characteristics of this population, models of treatment and treatment outcomes.