The International Journal of Psychosocial Rehabilitation
Determinates of mental illness severity
Christopher Alan Griffiths

Senior Research and Evaluation Fellow
Northamptonshire Healthcare NHS Foundation Trust
 Visiting Fellow
University of Northampton
Berrywood Hospital, Northampton

Griffiths CA (2017) Determinates of mental illness severity.
nternational Journal of Psychosocial Rehabilitation. Vol 21 (2) 31-34

The severity of mental illness has implications for the person experiencing the mental illness, their family and friends, clinicians working with them, service providers, and wider society. However, there is no definition or measure which considers all of the factors associated with mental illness severity. A holistic view of severity is required to understand the full impact of a mental illness and enable effective support, care, treatment, and mental health promoting societies and environments.

Key Words:  Severity, mental illness, recovery

The presence of mental illness is determined by interrelated biological, psychological, social, cultural, and environmental factors. There are a various definitions of mental illness that are referred to in academic literature, and there is no single internationally agree definition of severe mental illness (Ruggeri, 2000). The term severe mental illness is generally used to refer to psychotic disorders and bipolar disorder (Mental Health Foundation, 2015). However, a person may have another mental illness diagnosis, for example, depression or anxiety, and it can be a severe mental illness for that individual.

Definitions of mental illness which are referred to in academic literature include the US surgeon general’s: “Mental illness is the term that refers collectively to all diagnosable mental disorders. Mental disorders are health conditions that are characterized by alterations in thinking, mood, or behavior (or some combination thereof) associated with distress and/or impaired functioning” (U.S. Department of Health and Human Services, 1999, p. 4–5). Therefore, mental illness severity could be considered to be the degree of alteration in thinking, mood, or behaviour, or degree of distress and impaired functioning. The World Health Organisation (2004, p.10) does not define mental illness but defines mental health: “Mental health is defined as a state of well-being in which every individual realizes his or her own potential, can cope with the normal stresses of life, can work productively and fruitfully, and is able to make a contribution to her or his community.” Therefore, severity of poor mental health could be considered to be the degree of inability of a person to realise their potential to cope, work productively, and make a contribution to community.

Neither of these two widely used definitions seeks to define severity of mental illness and there is no generally agreed definition of severity of mental illness. Severity could be defined based on a range of factors: number of defined symptoms present (e.g. hallucinations, avolition, delusions); level of symptoms (e.g. frequency of hallucinations, level of avolition, number of delusions); number of mental illness diagnoses present (for example, meeting diagnostic criteria of co-occurring depression, schizophrenia, self-harm), degree that a person is able to self-manage their mental illness, and/or percentage of a person’s day affected by the mental illness.

Various manuals and measures are used to assess the factors that may determine the severity of mental illness. The most widely used diagnostic classification manuals are the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (DSM-5) (American Psychiatric Association, 2013), and the World Health Organisation’s International Statistical Classification of Diseases and Related Health Problems (ICD-10) (World Health Organization, 1992). These manuals do not list diagnostic categories in order of severity, and diagnosis does not efficiently measure impairment severity (Goldman & Grob, 2006). However, they have been used within the healthcare services to categorise people as having severe mental illness. In one example, the primary care Severe Mental Illness (SMI) register used within the United Kingdom’s NHS is defined with specific ICD codes. This includes, for example, schizophrenia (ICD-10 code: F20) and bipolar disorder (code:F31) and excludes many diagnosis including seasonal affective disorder (ICD-10 code: F33).

Clinicians and researchers use measurement tools that take into account factors that could be considered to be elements related to mental illness severity. A mental illness assessment and monitoring measure used in the NHS is Health of the Nation Outcome Scales Payment by Results (HoNOS PbR). There are 18 questions on which service users with mental illness are rated by clinical staff on a five point Likert scale ranging from: ‘no problem’ to ‘severe to very severe problem’. Questions include: ‘problems associated with hallucinations and delusions’, ‘problems with depressed mood’, ‘cognitive problems’, ‘non-accidental self-injury problems with activities of daily living’, ‘problems with occupation and activities’, ‘problem-drinking or drug-taking’. This information is used to place people in care clusters, these clusters are partially determined by severity of mental illness (Department of Health, 2013). The disadvantages of this approach is that it requires training to administer the assessment, it is a clinician’s view of a patient, and scores can vary due to differing clinician’s views of the same person: they can lack interrater reliability.

Severity can be viewed from the perspective of a clinician or the individual experiencing mental illness (Department of Health, 2013a). The concept of personal recovery (Anthony, 1993) has been adopted as a principle underlying many mental health services. The degree of recovery may be considered to be a proxy for severity. Recovery measures, such as the Questionnaire on the Process of Recovery (QPR) (Neil et al. 2009) or the Recovering Quality of Life (ReQoL) (Keetharuth et al. 2017), take into account factors that include social inclusion, developing positive social relationships, meaningfulness, motivation, personal agency, actively engaging with life, feeling better about oneself, feeling able to take chances in life, and assertiveness. Although a person may be considered to have a severe mental illness through clinical measures such as HoNOS, they may score themselves positively on a self-report measure of recovery. Mental illness severity is subjective.

Impact on quality of life can also be an indication of severity of mental illness. There are various measures of quality of life that may indicate severity, for example SF-36 (Ware & Sherbourne, 1992) is widely used (this has two sub-scales: mental and physical health related quality of life), and the NHS mental health dashboard employs the Social Care Related Quality of Life (SCRQoL) measure from the Adult Social Care Survey (ASCS). Using a four point Likert scale from ‘no unmet needs in a specific life area or domain (the ideal state)’ to ‘no needs met’, this asks people to provide answers to questions in seven areas: control, dignity, personal care, food and nutrition, safety, occupation, social participation, and accommodation.

Life satisfaction is an indicator of subjective or apparent quality of life (Veenhoven, 1996), and may be an indicator of the impact of severity of mental illness. The most widely used life satisfaction scale is The Satisfaction with Life Scale (Diener et al. 1985); which asks people for an overall judgement of their lives. Questions are: ‘in most ways my life is close to my ideal’, ‘the conditions of my life are excellent’, ‘I am satisfied with life’, ‘so far I have gotten the important things I want in life’, ‘if I could live my life over, I would change almost nothing’. The measure uses a seven point Likert scale from strongly disagree to strongly agree.

Impact on wellbeing may also be an indication of severity of mental illness. Self-reported wellbeing health is measured in the NHS mental health dashboard using the Warwick–Edinburgh Mental Wellbeing Scale (WEMWBS) (Tennant, et al. 2007). This is a positively worded self-report measure that includes questions related to optimism, feeling useful, feeling relaxed, dealing with problems well, thinking clearly, feeling close to other people, and being able to make decisions. Therefore, deficits on these factors could be a measure of severity of mental illness.

The level of psychological distress may indicate severity of mental illness. An example of a measure of psychological distress is the Kessler 6 (K6) for serious psychological distress (Kessler, 2003). Six factors (nervous, hopeless, restless or fidgety, so depressed that nothing could cheer you up, that everything was an effort, worthless) are assessed using a five point Likert scale  from ‘all of the time’ to ‘ none of the time’.

People’s ability to self-manage their mental illness may also be a measure of mental illness severity. An example of a measure used by clinicians and researchers of an individual’s perceived ability to manage illness and health behaviours is the Patient Activation Measure (Hibbard et al. 2004). Highly activated patients are more likely to have better clinical outcomes and lower rates of hospitalisation. Patients with low activation levels are more likely to attend accident and emergency departments, be hospitalised or be re-admitted to hospital - leading to higher health care costs (Hibbard & Gilbert, 2014).
In addition to viewing severity from the perspective of the clinician, individual and mental health service providers, severity can also be viewed from the perspectives of family, caregivers and/or friends of the individual, and the wider society in which the person lives. Mental illness of an individual can have an impact their family, caregivers and/or friends which can vary in severity of impact. Society benefits from the contribution of individuals (for example: taxes, voluntary work, and care and support for others), and the severity of impact of these factors can, to varying degrees, be negatively affected by individual’s mental illness.

In conclusion, clinicians and researchers have sought to define mental illness, mental health, or the factors related to mental illness or having mental health, and developed manuals and measures that capture these definitions. Mental illness severity can be viewed from the point of view of the individual experiencing mental illness; services providing care, treatment and support; friends, caregivers and/or relations; or society. If a measure is chosen by researchers or clinicians to represent severity, then it is the contents of that particular measure that determines the definition of severity in that case. There is not currently a measure of severity that seeks to take into account all the possible severity related factors.


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