ChemMatters | DECEMBER 2017/JANUARY 2018 15
serotonin reuptake allows enough serotonin
to be transmitted to the next neuron, restoring
proper neural circuitry (Fig. 2).
SSRIs that you may have heard of include
Prozac, Paxil, and Zoloft. They use this mecha-
nism to increase extracellular serotonin levels.
Another class of antidepressant drugs are
known as monoamine oxidase inhibitors
(MAOIs). Monoamine oxidases are enzymes
that are also present at synaptic terminals,
and they perform oxidative deamination on
neurotransmitters. These enzymes use oxygen
to remove an amine group, plus the adjacent
hydrogen atom, from a target molecule, which
results in the corresponding ketone or aldehyde
and ammonia.
MAOIs inhibit the activity of monoamine
oxidase to prevent the breakdown of monoamine neurotransmitters and increase their
availability. In this way, more neurotransmitters are available in the synaptic terminal for
signal propagation.
Antidepressant side effects
Side effects of SSRIs may include suicidal
thoughts, appetite change, emergence of
nervousness, irritability, mood instability, and
sleepiness. When a teen experiences side
effects, he/she might be tempted to stop taking
medication rather than continue with medical help. It’s important to adhere to a doctor’s
guidance and attend all appointments. Doctors recommend that even when experiencing
side effects, teens should continue to take
antidepressants and consult a doctor about
their discomfort. Quitting SSRIs suddenly may
cause a worsening of depression and the dose
needs to be slowly tapered off to avoid severe
withdrawal symptoms.
Each person reacts differently to medication,
so doctors typically monitor newly diagnosed
patients carefully to make sure they are receiv-
ing the right dose of medication and treat-
ment; finding the right medication and dose
may take some trial and error. This requires
patience, as some medications need several
weeks or longer to take full effect and for side
effects to ease as the body adjusts.
Despite reported side effects, antidepressants are an effective form of treatment in many
patients, making them the standard of care to
treat depression. MAOIs are less commonly
prescribed because the side effects are more
severe than SSRIs, and they include insomnia,
dizziness, weight gain, and muscle aches.
Causes of depression
Research suggests that depression is
more nuanced than a simple chemical imbalance. Accordingly, antidepressants may have
farther-reaching biochemical consequences
in addition to restoring neurotransmitters
levels. In the past 10 years, several studies
have shown that by increasing the concentration of monoamines at the synaptic terminals,
antidepressants may encourage the growth of
new neurons.
Additionally, cultured cells exposed to an
SSRI allowed neurons to stick to one another,
as is required for the formation of synapses.
The presence of new neurons could increase
the efficiency of communication in this part of
the brain, which may lead to restored circuits
and to improved mood.
Overcoming depression
There are many chemical abnormalities
that occur in areas of the brain that control
mood. Low levels of key neurotransmitters
and low-functioning neural circuits are two
conditions associated with depression. The
best remedy for these involves a combination
of medication, psychotherapy counseling, and
the development of healthy habits, such as a
nutritious diet and exercise.
With this information, if you or someone
you know seems unusually down, you can
understand their symptoms from a chemical
perspective, and you may be able to provide
them with some advice, beyond just telling
them to cheer up.
SELECTED REFERENCES
What Causes Depression? Harvard Health
Publishing, Harvard Medical School: http://www.
health.harvard.edu/mind-and-mood/what-causes-depression [accessed Sept 2017 ].
Teen Depression. Mayo Clinic, Aug 17, 2017:
http://www.mayoclinic.org/diseases-conditions/
teen-depression/home/ovc-20164553 [accessed
Sept 2017].
Antidepressant Medications for Children and
Adolescents: Information for Parents and
Caregivers. National Institute of Mental Health,
https://www.nimh.nih.gov/health/topics/child-and-adolescent-mental-health/antidepressant-medica-tions-for-children-and-adolescents-information-for-parents-and-caregivers.shtml [accessed
Sept 2017].
Christine Scaduto is a science writer who lives
in Waltham, Mass. This is her first article in
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Serotonin tries
to be reabsorbed
ocks
ption
of serotonin
Synapse
Serotonin
is released
SSRI bl
reabsor
Presynaptic
nerve ending
Postsynaptic
nerve ending
Receptor sites
Figure 2. SSRIs work to block the reabsorption
of serotonin. Due to the action of SSRIs in
preventing the reuptake of serotonin, more
serotonin remains available to be transmitted to
the next neuron, restoring proper neural circuitry
and keeping extracellular serotonin levels higher.
