Mental health refers to our cognitive, emotional, behavioural and social well-being. There is no univocal definition of mental health, as it is subject to cultural norms, evolving knowledge and competing theories. In 2007 the World Health Organization (WHO) broadly defined mental health as a “state of well-being in which the individual realizes his or her own abilities, can cope with the normal stresses of life, can work productively and fruitfully, and is able to make a contribution to his or her community”. In this perspective, mental health involves more than the mere absence of mental illnesses and disabilities, but encloses such dimensions as emotional wellness, personal fulfilment, resilience and social bonding. In addition, mental health relies on constitutional aspects such as feelings of autonomy, mastery and control, perceived self-efficacy and self-esteem and a sense of purpose and meaning in life. 

In a nutshell, good mental health is altogether critical to individuals, families, schools, workplaces and communities. From a policy point of view, focusing on population mental health is prominent in achieving public health targets and societal goals.

Mental health is an integral aspect of our overall health and quality of life. In fact, physical, mental and social health are interdependent and interwoven strands of global health. On the one hand, mental illness affects our daily living, interpersonal relationships and physical health. On the other hand, stressful life events, social connections and physical conditions can may lead to mental health problems. Besides being valued for itself, mental health also yields protective effects against stress, unhealthy lifestyle habits, various physical illnesses and socio-economic inequalities. Maintaining and restoring mental well-being is thus crucial for a long and healthy life, as well as a healthy, prosperous society. 

Mental ill health refers to psychological difficulties that we can experience at certain times, that is, when the demands placed upon us exceed our resources and coping abilities. For example, high work pressure can cause poor concentration, irritability, mood swings and sleep disturbance. Such problems relative to a particular situation are usually temporary and respond to dedicated support, reassurance or first line counselling. Most often, the signs of mental health disruption include strain, distress, impaired functioning and debilitating symptoms, but do not meet the severity criteria for clinical mental illness. Mental health problems are common, appear at any stage of the life course and do not necessarily lead to mental illness or disorders. 

There is no clear line to distinguish mental health from mental illness: the thresholds and criteria used to determine mental disorders have been set by convention.
A mental disorder is diagnosed based on the intensity, impact and duration of a specific cluster of symptoms, characterised by alterations in cognition, emotion, mood or behaviour (or some combination thereof), with distress and impaired functioning. For example: 

• Depression is characterised by persistent sadness or despair, loss of interest in activities, social withdrawal and apathy. A depressive disorder is established if most symptoms are relatively severe and last for over two weeks. 
• Anxiety features feelings of fear or dread, restlessness, muscle tension, rapid heart rate and shortness of breath. These symptoms take the form of an anxiety disorder if they appear to be excessive or inappropriate with respect to given circumstances.

Several hundreds of disorders are inventoried and described in two major guidelines: 

1. the Diagnostic and Statistical Manual of Mental Disorders (DSM) published by the American Psychiatric Association, 
2. and the International Statistical Classification of Diseases and Related Health Problems (ICD), produced by the World Health Organization.

The diagnosis of a mental disorder requires multiple steps and is preferably consolidated by a psychiatrist, psychologist, or other mental health professional. Unfortunately, severe mental disorders often entail social exclusion, stigmatisation, discrimination or non-respect of rights and dignity. Poor mental health should be treated with the same urgency as physical health.

The causes of most mental disorders are not precisely known, but they involve the interaction between multiple genetic, biological, developmental, psychological, lifestyle, stress and social factors, of which the relative importance may vary. For example, schizophrenia is more strongly associated to genetic determinants, whereas post-traumatic stress disorder (PTSD) is triggered by exposure to an extreme event. But in both cases, personal experiences as well as psychological and social factors will influence the outcome and the expression of the disorders. Mental and behavioural disorders have their basis in the brain, a complex organ that ensures the interface between the inner genetic, molecular and biochemical information and the outer environmental information.

From a public health perspective, the large variation in the prevalence of most mental disorders between and within countries suggests that social determinants have particular salience. These include for instance parenting and education, interpersonal relationships, socioeconomic status, living conditions, cultural and religious context, stigma and social justice. In line with the WHO strategy (2008), a comprehensive approach is needed to tackle population mental health, which involves not only the provision of treatment and care, but also embraces non-health policy sectors that have a role in preventing a risky context for mental ill health. 

The competences for organizing mental health care in Belgium are shared between the federal authorities, the regions and the communities. Over the past decades, various reforms in mental health care have been implemented around three main target groups: 1) adults, 2) children and adolescents, 3) forensic psychiatry. These various reforms aim to strengthen community care in mental health as well as the collaboration within care networks. More information on mental health care in Belgium is available on the website For a healthy Belgium. Health care insurance in Belgium covers different types of mental health care (in and outpatient care) depending on the needs of the people. Information is available on the website of the National Institute for Health and Disability Insurance (INAMI-RIZIV).