First of all, I do not, of course, recommend meditation as an alternative to medication or to therapy.
Meditation is not a magic cure for all ailments, although it can help with many physical and emotional disorders. Although doctors do not always have all the answers, medical advice should be sought from a qualified practitioner if you suffer from severe depression, and it’s extremely unwise to stop taking prescribed medication without consulting a professional.
Medication may be needed to control severe depression, and medication will certainly be needed for bipolar disorder. Psychotherapy can also be very useful. For extreme depression, meditation should only be used as a complementary practice, although for more minor depression meditation can usefully be used alone.
Meditation is a term covering a wide variety of ways in which we can work directly or indirectly with our mental states to effect desired change. It is based on the recognition that with awareness we can to some extent choose how to respond to circumstances. We all have experience of this. You might realize that you are getting impatient and irritable, and decide to relax, letting go physically and emotionally.
Two things are going on here: one is the awareness of our mental states, and the second is the ability to make choices that shift our mental states in a desired direction. Meditation both helps us to become more aware and offers us techniques to help us choose alternative responses (and therefore experiences).
The choices that we can make are always limited, and the effects they have may be small, but they are incremental and supplemental — that is they add up over time to create more profound changes in our outlook and in our ability to make more effective choices in the future. The choices we can make when we are depressed are definitely more limited than otherwise, but such choices do exist.
So learning meditation implies two things: the cultivation of awareness, so that we can make such choices more often and more easily; and learning methods that allow us to alter our mental states. Such methods are often very simple – things like being aware of your breathing low down in your body to calm yourself when you are anxious.
Although meditation is not a cure-all, it obviously has applicability to those who suffer from depression since it is connected with learning to move from undesired states (including depression) to more desired states that are more pleasant and fulfilling and allow more normal functioning.
Every person who learns to meditate is a unique individual. Each person works with a unique pattern of conditioning, which affects his or her ability to be able to be aware and to effect change. There are varying internal and external factors that affect our meditation (from ingrained habitual mental states to the effect of our work and our environment), and these are more or less easy to work with.
We are all working with (and to some degree against) our conditioning. Those who suffer from depression have to contend with chemical imbalances that have a strong effect on mental functions. Sometimes those chemical imbalances are short-lived and due to circumstances, diet, or even lack of sunlight (my own periods of depression have always happened in the winter months).
Other times they may be caused by genetic factors. But to my mind this just makes it more essential that people in this situation use every means available to ameliorate the effects that their body chemistry has on their mental and emotional functioning. You can’t change your genes, but there are things you can change.
Buddhism teaches that all positive change starts with dukkha, which means unsatisfactoriness or even suffering. No matter the source of your depression, your depression is the best reason you have to start meditating.