What is psychiatric illness?
This explanation is primarily to eliminate the mystery associated with psychiatric illnesses. There is far more information available today about the functioning of the brain and causes of psychiatric illnesses compared to earlier years. However, most people are not aware of them. As a result, psychiatric illnesses are considered a mystery even now by most people.
It is important to know that you are not alone with a psychiatric illness. About 1 out of 20 or 5% of the population anywhere in the world will get psychiatric illness during their life, whether they are rich or poor, educated or uneducated, or they live in slums or palaces. In developed countries, about 60% of these persons with psychiatric illnesses receive medical treatment. In India far less number of people take treatment (7%) because they are ignorant about modern methods of treatment or they have a fear of being branded as a 'mental patient'. Physicians in India also find it difficult to diagnose psychiatric illness in the early stages because of their limited training in psychiatry.
Not getting treated early has high costs for the patient and his family. His efficiency is lost resulting in poor productivity, poor earning capacity, loss of job, family disturbances, social inadequacy, and branding, finally dragging him and his family down the socio-economic scale and respectability. Beyond all this, there is also higher risk of suicide in untreated patients with psychiatric illness.
The most difficult aspect of understanding a psychiatric illness is to know that 'he can control his thoughts'. In reality 'he can control substantially what he thinks, but it is difficult to control How he thinks'. The content of what you think is based on your life experiences, while how you think depends on inherited patterns of thinking.  In psychiatric illnesses, these inherited patterns of thinking are altered into abnormal patterns due to chemical abnormalities in the brain. If a person's thoughts suddenly begin to change in it's 'form' into unusual patterns, it is likely that there is a change in the brain chemicals and may indicate the onset of a psychiatric illness. These changes make the person think in an uncontrollable fashion.  Thoughts keep coming without control.
What are the common misconceptions about psychiatric illnesses?.  Firstly, many people believe that psychiatric illnesses occur exclusively due to 'External stressful factors'. The most severe form of sadness occurs in normal people due to death of first-degree relatives. But he recovers from this severe sadness, usually within 3 months, by talking about the event to his kith and kin, and through culturally accepted modes of mourning ceremonies. He copes up with the loss, leading to well-adjusted behaviour in 3 months' time. This kind of reaction to stress is sometimes called 'Post traumatic stress disorder'. Other low-intensity stressors will result in low intensity and shorter duration reactions. Think of the millions of people who live in slums all over this country.  If external factors were to cause psychiatric illness every time, we would have had a psychiatrically sick country !! People who are normal, usually have an inherent capacity to learn how to cope with difficult situations.
Many people also believe that medical illnesses cause psychiatric illnesses. Many medical illnesses cause confusion. However, they are only symptoms of the underlying medical illness. For example, a bleed or tumour of the brain can cause some form of behaviour abnormalities. However, if the patient is treated for his medical condition he will recover from these behaviour abnormalities. These are not primary psychiatric illnesses.
we discussed earlier that a substantial part of behaviour is inherited. So one needs to know what is inherited ??? There are two distinctly different sets of behaviours that are inherited, namely 'Personality' and 'Psychiatric illnesses'.
Personality is how you describe 'what kind of a person you are'. A person can be very orderly or disorderly, he can be very quiet or outgoing, he can be a con man or a gentleman. All these are traits that sum up into  'yourself'. A very quiet person can get trained to become a good salesman for a company. He then meets different people, sells his products quite effectively and comes back to his house to become once again very quiet and introspective person. One can train himself to be like someone else for a period of time. However, he cannot change into some other personality in a sustained fashion effectively.' Personality' per se is not a psychiatric illness, and one cannot give medicine to change personality. Constant training, advice, counselling etc. may be useful to make some change, more often very temporarily.
Psychiatric illnesses are a set of illnesses caused by abnormal patterns of thinking and feeling, and they are substantially inherited even though the content of thinking and feeling expressed reflect many of the patient's experiences. It is important to know that psychiatric illnesses are inherited very much like Diabetes Mellitus, through gene level inheritance. Hence if a person is loaded with the genes for the illness, he develops it early. Most people develop it in the 20s and 30s. If they have less loaded with abnormal genes they develop the illness later in life. 
When we do a physical activity like speaking, writing, walking etc., the electrical activity of the brain cells is in action. If somethings go wrong to the electrical activity of the brain cells, a neurologist treats the patient. An EEG is used to identify the problem. If a structural problem occurs in the brain, a scan identifies the structural changes and a neurosurgeon treats the patient.
When we 'think' and 'feel' it is the chemical activity of the brain cells that are in action. In a psychiatric illness, the chemical activity of the brain cells becomes abnormal. It results in abnormal thinking and feeling. Diagnosis of these illnesses is usually made clinically since they are easy to diagnose. Sometimes psychological tests are carried out to make a diagnosis. Medical treatment is then started to correct this abnormality.  Different kinds of psychiatric illnesses affect different sets of brain chemicals and alter the patterns of thinking and feeling differently, and they are treated differently. 
Now that we know who is psychiatrically ill, the question is ' When should he be treated ?'. The answer to this question is very subjective! It depends on the patient and his significant other people who decide for him. A person is treated when he finds the illness a problem for himself or for other people around him. It is like deciding when to go to a doctor for a fever. If it is mild for short duration, you may ignore it. The only exception is when there is a suicidal risk.
The doctor also has to decide about the treatment strategies. Usually, most psychiatric treatments take few months to start showing results. However side effects can show up earlier, though they are not common.  Hence the doctor monitors the patient periodically to evaluate whether the benefits of the treatment far outweigh the disadvantages. If the disadvantages outweigh the benefits, the treatment may be changed or even stopped.
Till now we were dealing with the changes in the brain during psychiatric illnesses.  Let us now see what happens to the body during the illness. The brain is connected to different organs in the body through a set of nerves called 'Autonomic nervous system' (ANS). This is like an electrical main switch connecting to all lights and plugs in a house. The ANS acts by protecting a person from any threat originating from an external or internal source. When there is a threat, the ANS activates different organs in the body to function more energetically. In other words, ANS becomes hyperactive under 'stress'. However, once the stress is relieved the ANS returns to its original level of activity. You may have experienced this phenomenon when you were waiting for an interview or an exam or when you see a snake in front of you. The hyperactivity of the ANS gives the person the extra energy to deal with the stressful situation effectively. During this period the heart beats rapidly, blood pressure goes up, there is sweating, hands become cold and shiver, there is more acid secretion in the stomach, people breathe rapidly and they have to go to the toilet more often. All these are symptoms of 'anxiety' or at times wrongly called by many as 'stress'. They are in fact a response to 'stress'. However, if it is prolonged or if it becomes too severe, it damages the organs, just as a machine gets damaged if you run it beyond its capacity.
 What happens to ANS in psychiatric illnesses? During psychiatric illness the brain misinterprets a threat continuously, resulting in continuous ANS hyperactivity. This situation results in organ dysfunction apart from the high degree of anxiety. As a result, people develop symptoms of organ dysfunction. For example, they feel faster heart beats, palpitation, and high blood pressure. Similarly, other organs also get affected and they can experience cold extremities and tremors of hands, irritable bowel symptoms, frequent urination, rapid breathing etc. on a continuous basis without any obvious reason.
 Unfortunately, conventional medicines used in the treatment of psychiatric illnesses do not effectively reduce ANS hyperactivity. Hence, people with psychiatric illness need to start some form of 'relaxation exercises' without depending solely on the effectiveness of medicines to relieve their discomfort due to ANS hyperactivity. Walking for an hour is very effective relaxation exercise. Meditation and Yoga are other culturally understood forms of relaxation exercises. Every culture has some form of relaxation exercises with different names. One can choose what is appealing for oneself.  This is a lifestyle change one has to adopt to reduce the impact of the illness on the body or any other form of stress on the body. One has to maintain a changed lifestyle all through life too. If you need to know more about 'stress', 'stressors' and 'stress responses', you will find it in the section on "Stress" on this website.
Till now we discussed what happens to the brain and the body during psychiatric illness.  It is now time to look into the changes in behaviour during this period. For most people, it is difficult to understand the changes that occur in the person's brain when he is ill. Similarly, the changes in his body and the anxiety he experiences are not visible to others.
However, there are many visible changes that occur with the onset of a psychiatric illness. These can be clubbed together and called 'Maladjusted behaviours'. They look different in different people and do not fit into universal patterns. This is because maladjusted behaviours are a result of the attempts by a person to escape from the strange changes he perceives in his body and mind. So he behaves in such a way that he thinks will be most helpful to himself. These behaviours may be quite disturbing for others. On most occasions, others do not understand his actions, unless he explains them. Most of the time a patient with psychiatric illness refuses to explain the reasons for his behaviour because he gets worried about others misunderstanding him, being teased, abused or scolded. However, his reluctance to explain can result in 'Branding' the person as 'mentally ill', 'eccentric', 'odd', 'crazy', 'mad' and so on, and his treatment gets delayed. 
Branding has its own consequences. It has a negative connotation. If the branding lasts for a long time the person is stuck with the brand even after he recovers from the illness. This makes it very important for the person to start treatment early in order to avoid permanent branding. Branding also has other consequences. The person is no longer relied on or respected. His employability reduces. His social relationships break down. Finally, he slides down the socio-economic ladder.
What can one do to change maladjusted behaviour ??? The medicines do not directly change them effectively. Nevertheless one has to change them to 'Well adjusted behaviours'. If a person continues with maladjusted behaviour despite recovery from the illness after treatment, the society will reject him. The most effective way to make the change to well-adjusted behaviour is to educate the person on why he behaves in this fashion. He needs to be educated on why he had his illness, how it has changed his thinking and feeling, why his body functions differently and he behaves as he does now, and what are its consequences. He needs to know how he can be treated and what are the limits of recovery. He needs to also understand how he can change his maladjusted behaviours into well-adjusted behaviours with his own efforts.
Counselling is a method of assisting in this process. There are many forms of counselling, practiced by many different groups. The basic principles in counselling are 'Advice', 'Reward' and 'Punishment', very much like how you bring up your children to become adults. The reward and punishment is often experienced from the society's reactions towards the patient. Societal advice is, however, insufficient, since the society does not understand the patient and his behaviour. This is where a counsellor can assist because he is trained or has the experience in dealing with many such people to guide them.
Different counsellors have their own methods of counselling, and they come under different schools. But what makes the process successful are the patient's desire to accept the illness, his motivation to change, ability to build a rapport with the counsellor and the counsellor's desire to achieve results for his client. Many people can also make changes to their maladjusted behaviour themselves by reading through materials about the illness like you are doing now, and working to make appropriate changes themselves.
There are of course exceptions to the patterns that I have explained earlier, such as alcoholism and drug dependence, problems of children, problems of the aged, marriage and social problems etc. Much more will be found in the usual lists that are published by different classifying agencies.
However, the concepts illustrated in the earlier sections will help many people with psychiatric illnesses to understand their illness in a logical way. This will also help them gain greater confidence and faster recovery.