Professor Dave here, let’s get check out some disorders.
We’ve learned quite a bit about the brain in this series, so now it’s time to take
a look at what can happen when psychological function goes awry.
When this becomes severe enough to seek treatment, we call this a psychiatric disorder, and while
these can be difficult to diagnose, there are a few common ones that we are beginning
to understand, so let’s take a look at these now.
First let’s discuss schizophrenia.
This can be among the most difficult to diagnose, as the symptoms are complex and overlap with
other disorders.
They also change during its progression, and none of them are present in every case of
the disorder.
But let’s quickly mention them now.
First, the positive symptoms, or the ones that represent an excess of some function.
These include delusions, typically relating to being controlled or persecuted, or delusions
of grandeur.
Auditory hallucinations are also common.
Inappropriate affect, incoherent thought, and generally odd behavior are also symptoms.
Next the negative symptoms, or ones that represent a deficit in some function.
This includes a flat affect, reduction of speech and motivation, anhedonia, which is
an inability to experience pleasure, or catatonia, which involves remaining motionless for long
periods of time.
A patient exhibiting several of these symptoms for extended intervals would likely receive
a diagnosis of schizophrenia.
In terms of a cause for this disorder, it seems clear that there is a genetic basis,
given the hereditary aspect.
At the very least, the potential is inherited, while the onset likely depends on experience
and environmental factors.
The actual mechanisms by which genes act to produce the disorder are not yet known.
Many studies have examined a potential link between schizophrenia and levels of dopamine,
given that antipsychotic drugs exert their effects through their interaction with dopamine
receptors.
More specifically, we now know that this is achieved by the antagonism of dopamine receptors
in synapses, thus preventing dopamine from exerting its effects, only to be metabolized
in the synaptic space.
But the dopamine theory of schizophrenia has been refined quite a bit over the decades,
and continues to be studied today.
The relevant genetic mechanisms are also being studied, and it is believed that there may
be as many as several hundred genes that can confer risk for schizophrenia.
Next up are the affective disorders, or mood disorders, known as depression and mania.
Clinical depression is a condition that goes far beyond the blues we all feel from time
to time.
It is often experienced for no particular reason, and to a degree that interferes with
daily life.
Mania, on the other hand, is sort of like the opposite of depression, characterized
by impulsive and overconfident behavior, and extremely high energy.
Patients who experience alternating periods of depression and mania are said to suffer
from bipolar disorder.
Much like schizophrenia, there are clear genetic factors that contribute to the development
of affective disorders.
Stress and trauma can also be responsible for the onset of depression, although they
typically do not enhance the susceptibility towards affective disorders in those who are
not predisposed towards them.
Seasonal affective disorder, occurring during the winter, and postpartum depression, experienced
by some women after giving birth, are also affective disorders, although they have very
specific experiential causes.
It is thought that depression is generally caused by low levels of activity at serotonergic
and noradrenergic synapses.
Antidepressant drugs have been somewhat successful in combating depression.
These typically fall into one of a few categories.
Monoamine oxidase inhibitors are monoamine agonists, meaning they increase the levels
of neurotransmitters like serotonin and norepinephrine by inhibiting the enzymes that break them down.
Tricyclic antidepressants block the reuptake of these same neurotransmitters, again increasing
their levels in the synapse.
Selective monoamine reuptake inhibitors also block reuptake, and these are very common.
Finally, there are mood stabilizers.
These act against depression without increasing the potential for manic behavior, which other
drugs can sometimes do.
In addition to pharmacological treatments for depression, talk therapy treatments, such
as cognitive behavioral therapy, are linked with significant symptom improvements in randomized
clinical trials.
Cognitive behavioral therapy involves understanding the links between thoughts, feelings, and
behaviors, and correcting cognitive errors to help rewire one’s thought patterns.
A combination of medication and therapy is generally considered the most effective approach
to treating depression and other mood disorders.
Moving on to anxiety, this is a chronic fear that persists in the absence of any kind of
immediate threat, which compromises daily functioning due to avoidance of fear-triggering
stimuli.
When severe, this is considered a psychiatric disorder.
Varieties include generalized anxiety disorders, which are characterized by chronic worrying,
phobic anxiety disorders, which are triggered by exposure to specific objects or situations,
panic disorders, characterized by the rapid onset of fear and physiological stress symptoms,
which we commonly refer to as a panic attack, and obsessive-compulsive disorders, marked
by uncontrollable obsessive thoughts, and compulsive responses to those thoughts.
Posttraumatic stress disorder, or PTSD, is a pattern of distress, involving flashbacks
and avoidance of reminders, brought about following traumatic events, such as war or
sexual abuse.
Even when the onset is due to specific experiences, most anxieties do have a genetic component,
as one might expect.
Treatment for all of the above disorders typically involves cognitive behavioral therapy with
an exposure component, which essentially means confronting the situation or stimulus that
triggers the anxiety.
For example, someone who gets panic attacks in elevators would have to ride up and down
in an elevator a bit at a time to build tolerance to that situation.
Treatment can also involve drugs of a few categories.
Although they can be habit-forming, benzodiazepines are commonly used, as are selective serotonin
reuptake inhibitors, or SSRIs.
In addition, psilocybin, the active agent in hallucinogenic mushrooms, has shown promise
in clinical trials though it has not yet been FDA approved as of the filming of this tutorial.
Some act as agonists, some act as inhibitors, some act as positive allosteric modulators,
but a broader discussion of drugs used to treat psychiatric disorders, their mechanisms
of action, and the process by which clinical trials are performed, will have to wait for
the upcoming pharmacology series.
For now, let’s go ahead and keep studying the brain.