Depression is more than just a fleeting emotion. This illness hampers a person's daily functioning, negatively impacting their physical health. However, in most cases depression is treatable.

Types of depressions:

  • Major depression: a period of moderate to intense depression lasting more than two weeks.
  • Dysthymia: chronic low mood with moderate symptoms of depression.
  • Postpartum depression: experienced by some women after the birth of a child.
  • Depression with psychosis: when a depressed person loses touch with reality and has hallucinations (hears voices or sees people or things that are not really there) or delusions (beliefs with no basis in reality).
  • Seasonal affective disorder: depression typically triggered by weather conditions or a particular period of the year.

Who is affected?

  • 8% of adults experience depression;
  • Depression usually first appears in adolescence or young adulthood;
  • Depression can affect people of any age, race, or social background;
  • The healthcare costs and the loss of productivity, which may be associated with depression, are concerns for all of society.

Mini-Psych School videos

Chronic or episodic depression and burnout? (2011)
Depression and burnout (2009)
Hitting bottom - Chronic or episodic depression and burnout? A 2011 lecture by Mimi Israel (in French)
Hitting bottom - Chronic or episodic depression and burnout? A 2011 lecture by Mimi Israel (in French)
How Blue Is Blue? A 2009 lecture by Camillo Zacchia on depression-Part 1
How Blue Is Blue? A 2009 lecture by Camillo Zacchia on depression-Part 1

Watch other Mini-Psych School lectures.

Causes of depression

Depression is a condition that is often misunderstood by the general public. Is it a disease in the traditional sense? Is it simply a reaction to life events? If a reaction is normal in a given circumstance, is it any less of a problem?

In essence, depression can be seen as either a disease or as a reaction. The best way to understand depression is to understand the various causes and influences of our moods. To begin with we must appreciate that we are biological beings. Everything about us is in our brains: thoughts, memories, attitudes, moods, intelligence and all else that makes us human. One can therefore argue that all psychological problems are caused by biochemical imbalances.

On the other hand, our biochemistry has most certainly been influenced by our upbringing and our experiences. It is for these reasons that we must consider both internal and external processes in trying to understand depression.


Some forms of depression can be understood in the same way as any other disease. In such cases, there appears to be something wrong with how the brain is functioning. Brain chemistry seems to be altered in such a way as to have a major impact on mood, and these mood changes do not appear to be linked to any obvious external event. Bipolar depression, where moods can swing from profound states of depression to phases of mania where the person feels almost superhuman, is one example of what would generally be considered a medical disease.


Having said this, it is certainly possible, and indeed probable, that biological mechanisms affect all of us and are important contributors to all forms of depression, even when the brain is functioning normally. For example, although we do not have an exact understanding of how they affect us, we know that factors such as our hormonal and nutritional states do impact mood.

Innate temperament

If you’ve ever had more than one child or any number of siblings, you have seen how no two individuals have the same temperament. We are clearly all born with our own package of traits and tendencies. Some of us are more adventurous, others more hesitant. Some get angry easily while others have a tendency to take things in stride. In the same manner, some people generally seem to be happy most of the time while others tend to be serious and pessimistic.

Environmental influences

Our innate temperament is a major component of personality, but our traits are also affected in a significant way by our experiences. We are shaped by our family values, by our society’s culture and by every experience we have ever had. This unique blend implies that a particular situation can never be understood, or reacted to, the same way by any two individuals. 

Life-altering events

Although all events are experienced through our personal values and beliefs, some are so challenging that depression is almost inevitable. The death of a loved one, for example, will normally have a profound effect on all of us. Depression in these cases is considered a normal reaction but it is no less serious. Each individual copes differently. Although we may all require a significant amount of time before we can return to a relatively normal level of functioning, for some people the depression lingers and goes beyond what is normally observed.

A history of events

The vast majority of people who consult for depression do not do so as a result of a single event. They have often struggled with depressive symptoms on and off for much of their lives. They normally report a life-long history of real or imagined failures. Although a significant event may have triggered an episode of depression and pushed them to seek help, the vulnerability was most likely always present.

The Common Thread - Personality

The above-mentioned factors all contribute to that which defines us: our personality. Biochemical variables and innate temperament interact with our development. The result affects how we react to events around us. It is our understanding of these events and our reactions to them that makes some of us more vulnerable to depression than others

Some personalities are simply more prone to depression. Unassertive people, for instance, will often feel trapped in unsatisfying situations; perfectionists will always feel disappointed in themselves or upset with others; dependent individuals will often find themselves in situations where they may be taken advantage of. This is why we must try to understand our own personal patterns of behaviour in order to maintain mental health.

Research at the Douglas

The following Douglas scientists specialize in depression research:


[Depression: types and causes] [Burn-out: causes] [Depression or burn-out ?] [Depression or burn-out: treatment and prevention] [Depression in 0 to 5-year-olds] [Depression in young people]