- [Speaker] Major depressive disorder, which is sometimes
just referred to as depression, is characterized by
prolonged helplessness and discouragement about the future.
Individuals with this disorder have low self-esteem
and very powerful feelings of worthlessness.
They also lack the energy to do the things that
they used to enjoy, much less the things that they
have to do, or the things that they don't enjoy.
They tend to feel socially isolated,
and have trouble focusing on important tasks,
and have trouble making decisions.
And this low mood tends to pervade
all aspects of their life.
There are a number of physical symptoms
that also go along with depression.
Lethargy, so feeling fatigued.
Individuals with depression also tend to show
fluctuations in weight.
So either a lot of weight gain or a lot of weight loss.
And they might also have trouble sleeping,
or they might sleep too much.
And I think that these physical symptoms are often ignored.
Because in Western cultures like in the US,
we tend to think about depression in terms of moods,
or in terms of emotional states.
But for individuals in some Eastern cultures,
especially cultures where it might be seen as inappropriate
to delve into, or talk about feelings and emotions,
people in these cultures tend to think about depression
and experience depression in terms of these bodily symptoms.
And so it's really important that these aren't discounted.
Depression or depressive symptoms are the number one
reason people seek out mental health services.
And because of this, some people have taken to calling it
the common cold of psychological disorders.
And I like that term for some reasons
and I dislike it for others.
What I like about it is that it captures how pervasive
this disorder is.
It is estimated that 13% of men and 22% of women
worldwide, could meet the criteria for depression
at least once in their lives.
And one study has shown that as high as 31%
of college students might experience this disorder,
and these are really high numbers.
And so in that way I think that this term is appropriate.
However, I think that the term common cold doesn't really
capture the seriousness of this disorder.
Because depression isn't just feeling down once in a while.
And it's not feeling sadness or grief at appropriate times,
which is just a normal part of life.
And I think that this term kind of minimizes
that part of the disorder.
Depression can be triggered by a life event,
like a loss or a breakup.
But it doesn't have to be.
It also doesn't usually appear alone.
It is actually really common for individuals with depression
to have other disorders, such as anxiety disorders.
And I've been writing in this blue color to kind of
signify depression, but I'm kind of getting bored
with it now so, let me switch it up.
So there are a number of factors that may be involved
in depression, and I'm going to split them up
into three categories,
biological factors, psychological factors,
and socio-cultural, or environmental factors.
And let me take a minute to get all of that down, alright.
First of all, we know from family and twin studies
that there's a genetic component to depression.
And we also know from studies that use functional imaging
that individuals with depression show a decreased
activation in the pre-frontal cortex.
And this can be associated with the problems
with decision-making that people with depression
tend to have, as well as their difficulties
in generating actions.
Researchers have also found lower levels of activity
in the reward circuitry in the brain.
And this could help to explain why individuals
with depression might not find enjoyment in
the actions that they once found pleasurable.
Depression has also been associated with certain
neurotransmitters and neurotransmitter regulation.
And I'll abbreviate that here
by writing NT for neurotransmitter.
Research has suggested that individuals with depression
might have fewer receptors for serotonin and norepinephrine.
And I think that all of this research is amazing,
I think that it's really important.
And it's also really compelling, in a way that research
findings that include neuroscience typically are.
But with that said, I really want to caution you against
oversimplifying these biological factors.
To give an example about why I'm saying this,
I wanna talk about the relationship between a certain
serotonin transporter gene and depression.
And this gene is know as 5-HTTLPR, and I'll write that down.
And a lot of findings have shown that this gene
is involved in depression.
But in actuality, it is only associated with depression
if the individual with the gene
is in a stressful environment.
But the story doesn't actually end there.
It's actually even more complicated.
Because it turns out that if an individual with this
genetic feature is placed in a warm and positive
environment, they actually show a decreased
risk for depression.
And this is something that we don't totally understand yet.
We're still trying to figure out why this might be the case.
But importantly, I think that this really shows us
how complicated biological factors can be.
Let's move on to some psychological factors
that might influence depression.
One theory is based on the concept of learned helplessness.
And this theory supposes that if an individual is exposed
to aversive situations over and over again,
without any power to change or control them,
they might begin to feel powerless in a way
that might lead to depression.
So if someone is exposed to prolonged stress due to
family life, or bullying, or some other cause that they
don't have control over, their helplessness could
spiral out of control.
And they might stop trying to change their situation
because they perceive it to be completely helpless.
And that's a behavioral theory or way of
thinking about depression, but there are
cognitive theories about it as well.
And these theories tend to focus on thoughts
or beliefs that, with repetition, could trigger depression.
And while it's true that everyone has negative,
or self-destructive thoughts every once in a while,
generally we are able to step back from them,
and we're able to realize that what we're thinking
isn't completely logical.
But sometimes people can get
trapped in these thought patterns.
And they might put too much emphasis on negative thoughts
and actions and experiences.
And when they ruminate on these things,
when they turn them over and over in their minds,
it's possible that these cognitive distortions
might lead to depression.
Another cognitive theory about depression focuses on the
concept of attribution, or explanatory style.
Now as we go about our daily lives, we naturally try to
understand and explain the events that go on around us.
And when we do this, we can either attribute
the things we see to internal or external causes.
So is it something that I did or was it something
that happened because of something that is completely
out of my control?
Did I get a bad grade on a test because I didn't study?
That would be an internal cause.
Or did I get a bad grade because the teacher
made a really unfair test,
which would be an external cause.
Individuals with depression tend to attribute
negative experiences to internal causes.
So maybe they'll think that a friend didn't
call or text back because they are unlikable or unlovable.
And not because they were at the movies with their family
and maybe their phone was off.
In addition to this, they tend to see negative experiences
as being stable.
So they think that they'll continue to happen in the future.
And they also tend to think that they're global.
So they might assume that one friend not calling them back
somehow signifies that none of their friends like them.
And together these things, these internal attributions,
these stable attributions and global attributions,
these things form a pessimistic attributional style.
And it might make certain individuals particularly
vulnerable to depression.
And there are many other
psychological theories about depression.
Things that have to do with coping style or self-esteem.
But it can actually be hard to know whether these things
cause depression, or if they are the result of it.
So does a pessimistic attributional style
lead to depression or do people with depression
tend to have a pessimistic attributional style?
It isn't always clear.
Environmental and social-cultural factors can also
have a strong influence on depression.
Having a friend or partner or roommate with depression
can actually increase the likelihood that individuals
around them will also develop depression.
And although we don't know exactly why that is,
some researchers suggest that it might have
to do with co-rumination,
where friends talk about problems and negative events.
But instead of discussing how to solve them,
they focus on the negative emotions,
and dwell on future problems and occurrences.
And on some level, this is kind of normal.
It is perfectly normal for close friends to take on some
of the negative feelings of the other,
like being sad when they lose someone who was close to them,
or being angry if they were dumped by their partner.
This is just natural empathy.
But the same empathy that allows us to comfort our friends
when they're under stress, might also be the reason
that depression seems to spread.
We also know that individuals with a low socio-economic
status, especially those living in poverty,
are more likely to develop depression,
as are those who are struggling to keep a job,
or have just lost a job.
And there are other environmental factors as well,
social isolation, child abuse, even prejudice,
have all been implicated in causing depression.
And let's think about this in terms of prejudice.
If someone grows up in a household that has
negative feelings about homosexuality, and if they grow up
and begin to have same-sex attractions,
they've probably internalized the prejudice
after years of hearing it.
And this could lead to depression.
Alright, so stepping back for a second,
we said that we had biological factors,
psychological factors, and socio-cultural
and environmental factors.
And when we put all of these things together,
we get what is is referred to
as a biopsychosocial model of depression.
And this theory acknowledges that
all of these factors play a role.
So, some people are genetically predisposed
to the condition, but it only comes about if the situation
is right, or if we develop certain patterns of thinking.