What is Mental Illness?
We should first learn about what “mental” means before we get to know more about "mental illness”. Describing something as "mental" denotes that it is related to a person's thoughts, emotions, sensations, and behaviours etc.
We are likely to be diagnosed with "mental illness" if we experience significant changes in our thoughts, emotions, sensations, and behaviours etc., and that our personal, work and/or social functions are hindered by the above changes.
Common types of Mental Illness
Major Depressive Disorder and General Anxiety Disorder are two common mental illnesses.

Major Depressive Disorder
Major Depressive Disorder (as known as depression) is not merely about feeling “sad". Depression causes significant and continuous changes in individuals' emotions, behaviours and thoughts etc., and these changes intervene with patients' daily living and functioning.

General Anxiety Disorder
It is common for people to be anxious under certain situations, for instance, taking an examination, going for an interview or having a momentous meeting. However, people with General Anxiety Disorder experience a more constant and overwhelming type of anxiety which adversely affects different aspects of their daily life, later causing them to avoid certain events, occasions, or people etc.

Misinterpretations of Mental illness and people with Mental illness
A lot of people see people with mental illness as "crazy people" and "weirdos"; others think people with mental illness could not take care of themselves and have to depend on others to live, and are thus sympathetic towards people with mental illness. These are not necessarily true. As we have mentioned before, one can be mentally healthy even though he or she might be living with mental disorder, and a lot of the time people with mental illness do not show apparent symptoms. What is more is that different mental illnesses have different causes, and hence, everyone has a chance to experience mental illness regardless of their gender, age, socioeconomic status and nationality etc.

The community and we might have an urge to uncover some fixed, apparent characteristics of people with mental illness, and hence slowly form labels for people with mental illness in the community. Even though two people are diagnosed with same type of mental illness, they do not have the exact same experience in mental illness; not to mention the complexity of the causes and manifestations of mental illness. It is just like you and me, we might both be born and raised inHong Kong but still, we differ in a lot of aspects.
What causes mental illness?
Mental illness does not stem from a single cause but is usually caused by various interwoven factors. When we discuss the risk factors of mental illness, the three aspects below shall be the focus:
1. Physiology
including risk factors associated with systems in the individual’s body

Abnormalities in the nervous system
Imbalance of neurotransmitters (the chemical messenger in the brain, for example, serotonin affects sleep, emotion and appetite)
Brain damage or abnormalities in brain functions
Abnormalities in endocrine system
including risk factors related to an individual's thinking pattern, way of perceiving and coping strategies etc.
Way of perceiving: For example if an individual tends to think in a dichotomized way, or selectively attend to negative happenings, he or she might face higher level of stress and emotional distress. Ruminating, thinking in absolute terms or having a high standard towards things and own self also create overwhelming stress.

Suppression caused by various social factors, for instance, ethnicity, gender, socioeconomic status
Major change in life
Past experience (e.g. traumatic experience etc.)
Daily life stress
Our mental health is adversely influenced by bad weather (for instance, drought, flood, and air pollution etc.) especially when there is bad weather frequently, or that the bad weather causes more devastating results or is more long-lasting. These kinds of bad weather affect our mental health in the following three ways:
1. Severe and frequent natural disaster causes destruction to homeland which leads to anxiety, it could as well lead to chronic and severe psychological distress.
2. Higher possibility for physical injury and adverse physical health influence aggravate mental health.
3. Destruction to the environment which we depend on for socializing and living. *Climate change and mental health: A causal pathways framework (2010)