average rate of depression is 5%,
so would expect identical twins to
have a higher CR
McGuffin (1996) - investigated the CR of depressive
twins; found 46% CR for MZ and 20% CR for DZ
suggests that depression has a heritable component
Adoption studies
Wender (1986) - biological relatives of adopted
sufferers of depression are about 7x more likely than
their adopted relatives to have had major depression
however, can't generalise as not everyone is adopted
children are often placed in
adopted homes that are
similar to their birth family
confuses the issue of
genes and environment
if depression was
completely due to
genetic factors, then
the CR would be 100%
Comorbidity
a relationship between depression
and other psychological conditions
Kendler (1992) - a higher incidence of mental disorders
in twins when looking at depression and generalised
anxiety disorders rather than depression alone
Psychological: Cognitive Theories
Learned
helplessness
Seligman (1975) - first discovered learned helplessness in his
experiments on animals; dog was placed into a cage where one side
was an electrified floor; dog would receive a painful shock through the
floor and would quickly learn that to escape the shock he could jump
over the barrier; however if the barrier was too high for the dog to jump
then the dog soon accepted that the shocks were unavoidable and
passively accepted the shocks; when the barrier was lowered again and
escape became possible, the dog still did not try to escape
they had learned to be helpless
Seligman argued that this
is what happens in
depressed people
people experience several negative
life events, feel that they can't escape,
and learned to cope with it in that way
however, animals used so can't
generalise and ethical issues
Abramson (1978) developed on learned
helplessness; stated that people
respond to failure in a number of ways
attribute the failure to an...
internal cause (something within
them such as personality / skill)
external cause (other
people / circumstances)
cause of the failure is either...
stable (likely to continue)
unstable (might easily change)
attribute the failure to a...
global cause
(applying to a range
of situations)
specific cause
(applying to one
situation)
people with learned helplessness
= internal, stable, specific
Beck's theory
of depression
Negative self-schema -
negative feelings and info
that we have about ourselves
once we have a negative
self-schema, it becomes difficult
for us to interpret any new info
about ourselves positively
when a person encounters a new
situation that resembles the original
conditions when the schemas were
learned, they will interpret it negatively
Beck's cognitive triad -
negative self-schemas cause
us to view ourselves, the world,
and the future negatively
however, Lewinsohn
(1981) concluded that there
was no relationship
between negative thoughts
and irrational beliefs and
future depression
a strength - therapies based on
cognitive assumptions are quite
successful for depression