[00:07] Depression is the leading cause
of disability in the world.
[00:11] In the United States,
[00:12] close to 10% of adults 
struggle with depression.
[00:15] But because it's a mental illness,
[00:17] it can be a lot harder to understand
than, say, high cholesterol.
[00:21] One major source of confusion is
the difference between having depression
[00:25] and just feeling depressed.
[00:27] Almost everyone feels down
from time to time.
[00:31] Getting a bad grade,
[00:32] losing a job,
[00:33] having an argument,
[00:34] even a rainy day can bring on
feelings of sadness.
[00:38] Sometimes there's no trigger at all.
[00:39] It just pops up out of the blue.
[00:42] Then circumstances change,
[00:43] and those sad feelings disappear.
[00:46] Clinical depression is different.
[00:48] It's a medical disorder,
[00:49] and it won't go away 
just because you want it to.
[00:52] It lingers for at least 
two consecutive weeks,
[00:55] and significantly interferes 
with one's ability to work,
[00:58] play,
[00:59] or love.
[01:00] Depression can have a lot
of different symptoms:
[01:03] a low mood,
[01:04] loss of interest in things
you'd normally enjoy,
[01:06] changes in appetite,
[01:08] feeling worthless or excessively guilty,
[01:10] sleeping either too much or too little,
[01:13] poor concentration,
[01:15] restlessness or slowness,
[01:17] loss of energy,
[01:18] or recurrent thoughts of suicide.
[01:21] If you have at least five
of those symptoms,
[01:23] according to psychiatric guidelines,
[01:25] you qualify for a diagnosis of depression.
[01:28] And it's not just behavioral symptoms.
[01:31] Depression has physical manifestations
inside the brain.
[01:35] First of all,
[01:36] there are changes that could be seen
with the naked eye
[01:39] and X-ray vision.
[01:40] These include smaller frontal lobes
and hippocampal volumes.
[01:44] On a more microscale,
[01:46] depression is associated 
with a few things:
[01:49] the abnormal transmission or depletion
of certain neurotransmitters,
[01:53] especially serotonin, norepinephrine,
and dopamine,
[01:56] blunted circadian rhythms,
[01:58] or specific changes in the REM
and slow-wave parts of your sleep cycle,
[02:03] and hormone abnormalities,
[02:05] such as high cortisol and deregulation
of thyroid hormones.
[02:10] But neuroscientists still don't have
a complete picture
[02:12] of what causes depression.
[02:15] It seems to have to do with a complex
interaction between genes and environment,
[02:20] but we don't have a diagnostic tool
[02:21] that can accurately predict where
or when it will show up.
[02:26] And because depression symptoms
are intangible,
[02:28] it's hard to know who might look fine
but is actually struggling.
[02:32] According to the National Institute
of Mental Health,
[02:34] it takes the average person
suffering with a mental illness
[02:37] over ten years to ask for help.
[02:41] But there are very effective treatments.
[02:43] Medications and therapy complement
each other to boost brain chemicals.
[02:47] In extreme cases,
electroconvulsive therapy,
[02:50] which is like a controlled seizure
in the patient's brain,
[02:53] is also very helpful.
[02:55] Other promising treatments,
[02:56] like transcranial magnetic stimulation,
[02:59] are being investigated, too.
[03:01] So, if you know someone 
struggling with depression,
[03:04] encourage them, gently, to seek out
some of these options.
[03:08] You might even offer to help
with specific tasks,
[03:11] like looking up therapists in the area,
[03:13] or making a list of questions
to ask a doctor.
[03:16] To someone with depression,
[03:17] these first steps can seem insurmountable.
[03:20] If they feel guilty or ashamed,
[03:23] point out that depression 
is a medical condition,
[03:25] just like asthma or diabetes.
[03:27] It's not a weakness 
or a personality trait,
[03:30] and they shouldn't expect themselves
to just get over it
[03:33] anymore than they could will themselves
to get over a broken arm.
[03:36] If you haven't experienced 
depression yourself,
[03:39] avoid comparing it to times
you've felt down.
[03:42] Comparing what they're experiencing
to normal, temporary feelings of sadness
[03:46] can make them feel guilty for struggling.
[03:49] Even just talking about 
depression openly can help.
[03:52] For example, research shows that asking
someone about suicidal thoughts
[03:57] actually reduces their suicide risk.
[03:59] Open conversations about mental illness
help erode stigma
[04:03] and make it easier 
for people to ask for help.
[04:06] And the more patients seek treatment,
[04:08] the more scientists will learn
about depression,
[04:10] and the better the treatments will get.