Classification of disorders

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Key Points

  • Disorders represent particular combinations of signs and symptoms that are grouped together to form criteria. A certain number of criteria need to be met within a certain timeframe for a person to be diagnosed as having a  disorder.
  • Not all AOD workers are able to formally diagnose the presence  or absence of mental health disorders. Diagnoses of mental health disorders should only be made by suitably qualified and trained health professionals.
  • It is nonetheless useful for all AOD workers to be aware of the characteristics of disorders so that they are able to describe and elicit information about mental health symptoms when undertaking screening and assessment, and to inform treatment planning.
  • It is important that clients suspected of having a comorbid mental health condition undergo a medical assessment as many symptoms of mental health disorders mimic those of physical disorders.

This chapter provides a brief overview of the mental disorders most commonly seen among clients of AOD treatment settings. Not all AOD workers are able to formally diagnose the presence or absence of mental health disorders. Diagnoses of mental health disorders should only be made by suitably qualified and trained health professionals (e.g., registered or clinical psychologists, and psychiatrists). It would be unethical for non-trained workers to use diagnostic labels in clinical notes, or to inform the client that they have a diagnosis, unless they have received written confirmation from a suitably qualified professional.

It is nonetheless useful for all AOD workers to be aware of the characteristics of disorders so that they are able to describe and elicit information about mental health symptoms when undertaking screening and assessment (discussed in Chapter B2), and to inform treatment planning. Many more people will present with some symptoms than will meet criteria for a diagnosis of a disorder; however, these symptoms are distressing and need to be managed nonetheless. It is hoped that the descriptions provided here will increase AOD workers’ knowledge and awareness of different signs (i.e., what is objectively visible about the client, such as sweating) and symptoms (i.e., what the client describes, such as sadness) of disorders. The case studies provided throughout these Guidelines also provide examples of how symptoms may present in clients with comorbid mental health disorders.

Disorders represent particular combinations of signs and symptoms that are grouped together to form criteria. A certain number of criteria need to be met within a certain timeframe for a person to be diagnosed as having a disorder. There are two main classification systems used to diagnose mental health disorders:

  • The Diagnostic and Statistical Manual of Mental Disorders, currently in its fifth edition (DSM-5) [24].
  • The International Classification of Diseases, currently in its 10th revision (ICD-10) [112].

These systems are similar; however, there are a number of important differences. The disorder descriptions outlined in this chapter are based on those provided by the most recent diagnostic manual available, the DSM-5, which was released in May 2013 [24]. AOD workers are encouraged to familiarise themselves with the DSM-5, in particular its uses, limitations and recommendations regarding differential diagnosis (i.e., determining which symptoms are attributable to which disorder).

It is important to note that substantial revisions to diagnostic and classification criteria have been made for many mental disorders, and the disorder descriptions may vary greatly from those in the previous edition (DSM-IV-TR [23]). In an effort to help navigate the major revisions, the primary changes between the DSM- IV-TR and the DSM-5 disorder classification are explained. As many AOD workers may also use ICD codings, we have cross-referenced the DSM-5 disorders described here with the corresponding ICD-10 codes in Appendix D. 

In these Guidelines we focus on 10 categories of disorder that are most commonly seen among people with AOD use disorders:

  • Attention-deficit/hyperactivity disorder (ADHD).
  • Schizophrenia spectrum and other psychotic disorders.
  • Bipolar disorders.
  • Depressive disorders.
  • Anxiety disorders.
  • Obsessive-compulsive disorder (OCD).
  • Trauma-related disorders.
  • Feeding and eating disorders (ED).
  • Personality disorders.
  • Substance-induced disorders.

There are, however, a number of other disorder types that individuals with AOD use disorders may experience. These include somatoform disorders, sleep disorders, and adjustment disorders. For further information on these disorders readers are referred to the DSM-5 [24].

It is also important to note that many symptoms of mental health disorders mimic those of physical disorders. For example, heart palpitations may be related to anxiety, or they may be a symptom of a heart condition. Similarly, depressed mood may be a symptom of major depressive disorder, or it may be a symptom of hypothyroidism. For this reason, it is important that clients suspected of having a comorbid mental health condition undergo a medical assessment to rule out the possibility of an underlying physical condition. This is particularly pertinent for those individuals with advanced AOD use disorders, who may suffer from malnutrition or organ damage.