Depression Concept Map | Pathophysiology | Etiology | Treatment | Antidepressants Mechanisms of Action

Depression (Major Depressive Disorder) Map: An Overview


This concept map covers the key points about (Depressive Disorders) including: definition, depression types, depression etiology, depression pathophysiology, diagnosis of depression, treatment of depression.
What is depression?
What causes depression?
What are the signs and symptoms of depression?
Non pharmacological treatment for depression
Pharmacological treatment of depression

Depression Concept Map
Depression Concept Map
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What is Depression?

The map starts with the definition of depression which is a mood disorders that affects patient’s cognition, behaviour, and physical functioning.  Depression is classified according to symptoms and course of the disease into:
  • Major depressive disorder / Major depression / Unipolar depression
  • Dysthymia
  • Postpartum Depression
  • Seasonal Affective Disorder (SAD)
  •  Depressive disorder not otherwise specified
  •  Mixed anxiety-depression
The main type of depression and the focus of this map is Major depressive disorder (Clinical Depression)

What causes depression?

Depression etiology

It is of unknown cause, but involves hereditary, social, developmental, and biological factors.  It is related to changes in brain monoamine neurotransmitters: norepinephrine (NE), serotonin (5-HT), and/or dopamine (DA).

Depression pathophysiology

Although depression is a disorder of unknown cause, many hypotheses have tried to explain the pathophysiology of depression.  Among the most prominent of these hypotheses are those mentioned in the following map of (Phathophysiologic Hypotheses of Depression):
Phathophysiologic Hypotheses of Depression
Phathophysiologic Hypotheses of Depression - Click on the image to enlarge
 The first one is “Catecholamines Hypothesis” which proposes that depression is linked to decreased brain levels of the neurotransmitters norepinephrine (NE), serotonin (5-HT), and/or dopamine (DA).  But it has been observed that the administration of antidepressants causes immediate increase in the synaptic levels of monoamines (NE and 5-HT) producing antidepressants adverse effects, while the antidepressive effects are not observed until after few weeks of dosing.  That observation is explained by the second hypothesis which is (Receptor Sensitivity Hypothesis).
According to “Receptor Sensitivity Hypothesis,” the decrease in NE and 5-HT results in low stimulation of the postsynaptic receptors by these monoamines, and consequently increased postsynaptic receptors' sensitivity and number.  That is how long term administration of antidepressants is responsible for decreasing the sensitivity "desensitization" and the number "down-regulation" of central β-adrenergic receptors and finally producing the antidepressant effect.
Concerning the third hypothesis which is called “The Permissive Hypothesis,” the control of emotional behavior results from a balance between NE and 5-HT, i.e. the decrease in both 5-HT and NE causes depression, while the decrease in 5-HT with an increase in NE causes mania.
This map provides you with the basic knowledge to understand the nature of the disease.  In the upcoming full map of (Depression), I will link between “Depression pathophysiology” and:
  •  how antidepressants work (i.e. mechanisms of action) and
  • what adverse effects they produce 

Diagnosis of depression

In case of suspected major depressive episode:
-          exclude bipolar depression; as major depression is a unipolar disorder.
-          exclude general medical illness, drug therapy, or substance abuse, that is why patients should undergo physical examination, mental status examination, basic laboratory work-up (CBC, thyroid function tests, and electrolyte determinations).
-          -         determine depression case severity using psychometric rating instruments as Hamilton Psychiatric Rating Scale for Depression (HAMD)

What are the signs and symptoms of depression?

DSM-IV-TR Criteria for Major Depressive Episode

A. Five (or more) of the following symptoms occur most of the day nearly every day for the same 2-week period;
     representing a change from previous functioning; at least one of the symptoms is either
     (1) depressed mood or (2) loss of interest or pleasure.

1. Depressed mood
2. Markedly diminished interest or pleasure in all, or almost all, activities
3. Significant weight loss when not dieting or weight gain (change of > 5% of body weight in a month), or
    decrease or increase in appetite
4. Insomnia or hypersomnia
5. Psychomotor agitation or retardation
6. Fatigue or loss of energy
7. Feelings of worthlessness or excessive or inappropriate guilt (which may be delusional)
8. Diminished ability to think or concentrate, or indecisiveness,
9. Recurrent thoughts of death, recurrent suicidal ideation with/without a specific plan or an attempt

B. The symptoms cause clinically significant impairment in social and occupational functioning
C. The symptoms are not due to effects of a substance (e.g., a drug of abuse, a medication),
     a general medical condition (e.g., hypothyroidism) mood-incongruent delusions or hallucinations
D. The symptoms are not better accounted for by bereavement (loss of a loved one)

Treatment of Depression

Nonpharmacological Treatment of Depression, includes:

  • Psychotherapy could be the first-line therapy in mild to moderate depression, but not used alone in case of acute severe and/or psychotic major depressive disorder.
  • Electroconvulsive Therapy (ECT) is safe and effective for severe mental illnesses, including all subtypes of major depression.  It is reserved for treatment-resistant cases and delusional depressions.
  • Light therapy.

Pharmacological Treatment of Depression

It should be understood on the basis of depression pathophysiology.  Antidepressants mechanisms of actions and accordingly adverse effects and –if present- drug interactions, contraindications, patient education, advantages, drug discontinuation symptoms and precautions of the following depression medications are stated in the map in the form of mini-maps for each antidepressant, linking between the key information about every medication of the following:

  • Selective Serotonin Reuptake Inhibitors (SSRIs): citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline
  • Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs): duloxetine, venlafaxine, desvenlafaxine
  • Norepinephrine-Dopamine Reuptake Inhibitors: Bupropion only
  • Tricyclic Antidepressants (TCAs) and Other Heterocyclics: amitriptyline, imipramine, nortriptyline, desipramine, amoxapine
  • Serotonin Modulators (5-HT2 blockers): nefazodone and trazodone
  • Alpha-2 Antagonist: Mirtazapine
  • Monoamine Oxidase Inhibitors (MAOIs): phenelzine, isocarboxazid, and tranylcypromine → nonselective (inhibit MAO-A and MAO-B), selegiline (transdermal patch) → inhibits only MAO-B at lower doses 
  • St. John’s.

Depression Concept Map Folded Poster

We hope you find Depression Concept Map helpful and we are looking forward to hearing your opinion. This map is available in the following forms:


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Depression Concept Map by Maha Atef, B Pharm
Last updated on: 13 June 2012

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