Medicines for depression: antidepressants

Antidepressants are medicines used to treat depression. The decision to take an antidepressant, undertake psychological therapy, or combine both approaches, is very individual. Talk to your doctor about what you think will work best for you.

Individual antidepressants can be grouped into different classes or groups, according to how they work chemically in the body. Within each group, there are usually several medicines which work in a similar way but may differ slightly from each other.

The different groups of antidepressants are about as effective as each other overall, but some people will respond to one antidepressant better than another. The type and severity of side effects can also be quite different between these groups of antidepressants. See How do the side effects of different antidepressants compare?

How do antidepressants work?

Serotonin is one of the neurotransmitters (brain chemicals) that transmit signals between cells in your brain. Serotonin, along with other neurotransmitters such as noradrenaline and dopamine, are thought to have an important effect on your mood. Different neurotransmitters control different functions — often more than one. The role of neurotransmitters in causing depression is not fully understood.

Antidepressants increase the amount of certain neurotransmitters, and this is how they are thought to reduce the symptoms of depression.

How effective are antidepressants?

About 50% of people taking antidepressants find their depression symptoms are halved. Antidepressants reduce symptoms such as:

  • feeling sad, hopeless or worthless
  • feeling excessively guilty
  • feeling suicidal
  • sleep problems (insomnia)
  • problems doing your usual work or hobbies
  • difficulty concentrating
  • restlessness
  • anxiety
  • loss of appetite.

Antidepressants are more effective for reducing symptoms in people with moderate or severe depression, rather than mild depression. Psychological therapies, such as CBT, are more effective than antidepressants for mild depression, and about equally effective for moderate depression, although the effects of CBT may last longer. Antidepressant therapy is advisable if you have severe depression; psychological therapies may be useful once you start to feel better.

As with all medicines, there is a placebo effect with antidepressants — this means some people who took a placebo (an inactive, or sugar, pill) in clinical trials also felt better. In trials of antidepressant use, about 30% of the placebo group found their symptoms were halved. This doesn’t mean antidepressants don’t work — but suggests there are several factors involved.

Placebos can have an effect because of the expectation of getting better, and because of other factors such as talking to the staff running the clinical trial. It may also be that some people improve over time anyway, regardless of treatment. This could be the case particularly with trials which recruited people with mild depression. Read more about placebos and clinical trials.

For more information

  • Malhi GS, Parker GB, Greenwood J. Structural and functional models of depression: from sub-types to substrates. Acta Psychiatr Scand 2005;111:94–105.;jsessionid=653DA568E96E2A126D014A4E1C5AC5B4.d01t04 (accessed 22 February 2012).
  • Williams JW Jr, Mulrow CD, Chiquette E, et al. A systematic review of newer pharmacotherapies for depression in adults: evidence report summary. Ann Intern Med 2000;132:743–56. (accessed 22 February 2012).
  • National Collaborating Centre for Mental Health. Depression: the NICE guideline on the treatment and management of depression in adults (updated edition). London: National Institute for Health and Clinical Excellence, 2010. (accessed 9 February 2012).
  • Psychotropic Expert Group. Therapeutic Guidelines: Psychotropic, Version 6. In: eTG complete [Internet]. Melbourne: Therapeutic Guidelines Limited; 2008. (accessed 9 February 2012)
  • Rossi S, ed. eAMH [online]. Adelaide: Australian Medicines Handbook, 2012. (accessed 22 February 2012)