Individuals affected with depression usually experience several bouts of depressive episodes. The symptoms almost occur every day and gradually begin interfering with the daily activities of the individual. The following are the signs and symptoms exhibited [6]:

• Too little sleep or excessive sleeping
• Loss of appetite accompanied by weight loss in some, while increase in appetite and weight gain in others
• Low level of mood characterized by loss of interest in normal activities
• Lack of energy, fatigue and difficulty in carrying out simple tasks
• Angry outbursts and feeling of irritation and frustration
• Poor concentration and inability to make decisions
• Feeling of worthlessness that causes suicidal thoughts and suicidal attempts
• Unexplained physical ailments such as back ache and headache

• Pain

  Depressive disorders may constitute a risk factor for vulvodynia and occur as a secondary condition to pain. [ncbi.nlm.nih.gov]

  You're in pain. Depression and pain share some of the same biological pathways and neurotransmitters. About 75% of people with depression suffer recurring or chronic pain, research shows. [prevention.com]

  "What TMS is doing is changing how that network functions, really rebooting the network to improve symptoms of mood, anxiety and chronic pain,” Leuchter said. [foxnews.com]

  In younger children, symptoms of depression may include sadness, irritability, clinginess, worry, aches and pains, refusing to go to school, or being underweight. [mayoclinic.org]

  Changes in Activity or Energy Level Physical Changes Caused by Depression Unexplained aches and pains Weight loss or gain Decreased or increased appetite Psychomotor agitation or retardation Emotional Pain of Depression Prolonged sadness Unexplained, [verywell.com]

• Fatigue

  OBJECTIVE: Fatigue after acquired brain injury may be related to the subcortico-frontal attention network. Depression is also strongly related to fatigue. [ncbi.nlm.nih.gov]

  Unfortunately, people who have chronic fatigue syndrome may become depressed. And while depression doesn’t cause chronic fatigue syndrome, it can certainly cause increased fatigue. [healthline.com]

• Weight Gain

  […] loss (short-term), weight gain (long-term), discontinuation syndrome*, forgetfulness, blunting of emotions, and easy bruising Toxicity due to overdosage is less serious than that with other antidepressants. [merckmanuals.com]

  Lidia’s diet consisted of fast food and soda but after noticing her weight gain was affecting her relationship with her husband, Lidia decided enough was enough and she started weight training. [youtube.com]

• Weight Loss

  Physical health was determined based on information regarding falls and weight loss and an assessment of each patient's general medical condition. The treating physician evaluated current suicidality in a comprehensive and standardized way. [ncbi.nlm.nih.gov]

  Changes in Activity or Energy Level Physical Changes Caused by Depression Unexplained aches and pains Weight loss or gain Decreased or increased appetite Psychomotor agitation or retardation Emotional Pain of Depression Prolonged sadness Unexplained, [verywell.com]

  How often have you been bothered that you have poor appetite, weight loss, or overeating over the last two weeks? NOT AT ALL SEVERAL DAYS MORE THAN HALF THE DAYS NEARLY EVERY DAY 5. [depression.org.nz]

  thinking, or making decisions Changes in appetite that lead to weight loss or gain Uncontrollable crying Headache Stomach ache Digestive problems Problems with sexual function Thoughts of death or suicide Attempting suicide If you or someone you know [my.clevelandclinic.org]

  headache, weight loss (short-term), weight gain (long-term), discontinuation syndrome*, forgetfulness, blunting of emotions, and easy bruising Toxicity due to overdosage is less serious than that with other antidepressants. [merckmanuals.com]

• Weakness

  CASE: A 42-year-old, right-handed male, presented with acute aphasia and right arm weakness. Urgent CT/CT-angiogram were normal except for an incidental hypoplastic right anterior cerebral artery (ACA) A1 segment. [ncbi.nlm.nih.gov]

  Some people believe that depression is a weakness and are reluctant to tell anyone that they are experiencing sadness or other symptoms. The absence of emotion may be interpreted as indifference rather than depression. [merckmanuals.com]

• Overeating

  High-dose intravenous treatment with methylprednisolone over 5 days and oral dose reduction over 3 weeks led to the sustained improvement of clinical symptoms. [ncbi.nlm.nih.gov]

  How often have you been bothered that you have poor appetite, weight loss, or overeating over the last two weeks? NOT AT ALL SEVERAL DAYS MORE THAN HALF THE DAYS NEARLY EVERY DAY 5. [depression.org.nz]

• Loss of Appetite

  The following are the signs and symptoms exhibited: Too little sleep or excessive sleeping Loss of appetite accompanied by weight loss in some, while increase in appetite and weight gain in others Low level of mood characterized by loss of interest in [symptoma.com]

  reduced energy and vitality; slowness of thought or action; loss of appetite ; and disturbed sleep or insomnia. [britannica.com]

  Symptoms: Sadness and or irritability Loss of interest or pleasure in everyday activities Loss of appetite—or increase in appetite Sleep disturbances—either insomnia or excessive sleeping Agitation or slowing in behavior Fatigue Feelings of worthlessness [nationalmssociety.org]

  Even the loss of appetite often seen in depression could be viewed as promoting analysis because chewing and other oral activity interferes with the brain’s ability to process information. [scientificamerican.com]

  Symptoms of depression may be different or less obvious in older adults, such as: Memory difficulties or personality changes Physical aches or pain Fatigue, loss of appetite, sleep problems or loss of interest in sex — not caused by a medical condition [mayoclinic.org]

• Nausea

  Melatonergic antidepressant Agomelatine Headache, nausea, and diarrhea Agomelatine has fewer side effects than most antidepressants. It does not cause daytime drowsiness, insomnia, weight gain, or sexual dysfunction. [merckmanuals.com]

  The present report discusses the case of a 70-year-old woman admitted to our institution due to sudden-onset nausea and vomiting. [ncbi.nlm.nih.gov]

• Constipation

  Clomipramine Desipramine Doxepin Imipramine Maprotiline Nortriptyline Protriptyline Trimipramine Drowsiness, weight gain, increased heart rate and decreased blood pressure when a person stands (orthostatic hypotension), dry mouth, confusion, blurred vision, constipation [merckmanuals.com]

  Thus, some TCAs can produce dry mouth, blurred vision, constipation, and dizziness upon standing. The dizziness results from low blood pressure that occurs upon standing (orthostatic hypotension ). [medicinenet.com]

• Increased Appetite

  Changes in Activity or Energy Level Physical Changes Caused by Depression Unexplained aches and pains Weight loss or gain Decreased or increased appetite Psychomotor agitation or retardation Emotional Pain of Depression Prolonged sadness Unexplained, [verywell.com]

  Other symptoms of atypical depression include weight gain, increased appetite, sleeping excessively, a heavy feeling in the arms and legs, and sensitivity to rejection. [helpguide.org]

  They have an increased appetite, resulting in weight gain. They may sleep for long periods of time. They are excessively sensitive to perceived criticism or rejection. They may feel weighted down, as if they can hardly move their legs. [merckmanuals.com]

• Eczema

  Pain Cirrhosis Cocaine Codependency College Colon Cancer Colorectal Cancer Coming Out Crohns Disease Cymbalta Cystic Fibrosis Dads Dementia Depression Diabetes Diverticulitis Divorce Dizziness Down Syndrome Drug Dyslexia EDNOS Eating Disorder Ecstasy Eczema [depression.supportgroups.com]

• Tinnitus

  Single Dads Single Moms Single Parents Singles Skin Cancer Skin Picking Sleep Apnea Sleep Walking Smoking Social Anxiety Social Security Spina Bifida Stress Stroke Stuttering Suboxone Sugar Addiction Suicide Surgery Teen Testicular Cancer Thyroid Cancer Tinnitus [depression.supportgroups.com]

• Low Back Pain

  In a Canadian study published in the journal Pain, people with depression were four times more likely to have intense or disabling neck and low back pain than those who were not depressed. [prevention.com]

• Feeling of Worthlessness

  […] of guilt Feelings of worthlessness Loss of self-esteem Despair Hopelessness Helplessness Difficult Moods Associated with Depression Irritability Anger Worry/anxiety Pessimism Indifference Self-critical Changes in Thought Patterns due to Depression Inability [verywell.com]

  […] unable to meet expectations Difficulty concentrating, remembering details, and making decisions Feelings of worthlessness, hopelessness or guilt Persistent physical symptoms such as headaches, digestive problems or chronic pain that do not respond to [halfofus.com]

  […] self-talk lack of energy, or feeling fatigued having feelings of worthlessness or guilt having thoughts of self-harm or suicide feeling hopeless and helpless difficulty remembering things. [au.reachout.com]

• Anxiety Disorder

  Aim: To develop a visual screening tool for depression and anxiety disorders that is applicable across cultures and levels of education. [ncbi.nlm.nih.gov]

  Myths and Facts Recovery Is Possible What To Look For Anxiety Disorders Behavioral Disorders Eating Disorders Mental Health and Substance Use Disorders Mood Disorders Obsessive-Compulsive Disorder Personality Disorders Psychotic Disorders Suicidal Behavior [mentalhealth.gov]

• Low Self-Esteem

  Clinicians use low self-esteem as one possible symptom when they diagnose the psychiatric condition of major depressive disorder. They don't necessarily care whether low self-esteem causes the depression or vice versa. [language.chinadaily.com.cn]

  For example, depression is not loneliness, it's not low self-esteem, and it's not being sad or distressed for good reasons. Those are all important and serious issues too, and they should be discussed, but this is not the place. [reddit.com]

  These issues can cause feelings of negativity, low self-esteem and lack of control over life. Work overload. Often women work outside the home and still handle home responsibilities. [mayoclinic.org]

  Adding psychological treatment to medication may be helpful for managing negative thoughts and low self-esteem and finding better coping strategies. [cancer.net]

• Delusion

  Psychotic depression occurs when a person has severe depression plus some form of psychosis, such as having disturbing false fixed beliefs (delusions) or hearing or seeing upsetting things that others cannot hear or see (hallucinations). [nimh.nih.gov]

  Psychotic depression arises against a background of psychosis, which may involve symptoms of delusions, hallucinations, or paranoia. [britannica.com]

  Sometimes depressive episodes can get so severe that hallucinations or delusions are present, the person becomes catatonic, or they feel stuck in bed. This is known as Psychotic Depression. Postpartum Depression occurs after giving birth. [psycom.net]

  In very severe depression, psychotic symptoms may emerge, for example delusions, hallucinations, and disorganized thinking and speech. These require treatment with antipsychotic drugs. [msdmanuals.com]

• Social Isolation

  Although the criteria are similar to general diagnostic standards for major depression, they reduce emphasis on verbal expression and include irritability and social isolation. [alz.org]

  Other sources of stress, such as reduced income, a worsening chronic illness, a gradual loss of independence, or social isolation, may also contribute. [merckmanuals.com]

  The desire for social isolation, for instance, helps the depressed person avoid situations that would require thinking about other things. [scientificamerican.com]

  Depression is more than just sadness Symptoms are wide-ranging and typically include: Social isolation Anxiety Low motivation Low energy levels Low self-esteem Lack of interest in activities – even the ones you used to love How Neurocore’s depression [neurocorecenters.com]

• Headache

  Melatonergic antidepressant Agomelatine Headache, nausea, and diarrhea Agomelatine has fewer side effects than most antidepressants. It does not cause daytime drowsiness, insomnia, weight gain, or sexual dysfunction. [merckmanuals.com]

  RESULTS: A quick and complete abrogation of the depression ensued along with improvement of migraine headaches, insomnia, and chronic fatigue. [ncbi.nlm.nih.gov]

  Symptoms can include Feeling sad or "empty" Loss of interest in favorite activities Overeating, or not wanting to eat at all Not being able to sleep, or sleeping too much Feeling very tired Feeling hopeless, irritable, anxious, or guilty Aches or pains, headaches [medlineplus.gov]

• Insomnia

  Although there was partial improvement in the patient's mood and anxiety symptoms with antidepressant treatment, insomnia remained a persistent complaint despite adequate trials of different sleep medications. [ncbi.nlm.nih.gov]

  Psychostimulants Dextroamphetamine Methylphenidate Nervousness, tremor, insomnia, and dry mouth These drugs are usually used with antidepressants. Used alone, they are usually ineffective as antidepressants. [merckmanuals.com]

  Teen insomnia linked with depression, anxiety http://www.sciencedaily.com/releases/... Physical fitness can help prevent young adolescents' depression, study finds http://www.sciencedaily.com/releases/... [youtube.com]

• Agitation

  Common symptoms include: Changes in sleep Changes in appetite Lack of concentration Loss of energy Lack of interest in activities Hopelessness or guilty thoughts Changes in movement (less activity or agitation) Physical aches and pains Suicidal thoughts [nami.org]

  Changes in Activity or Energy Level Physical Changes Caused by Depression Unexplained aches and pains Weight loss or gain Decreased or increased appetite Psychomotor agitation or retardation Emotional Pain of Depression Prolonged sadness Unexplained, [verywell.com]

  Norepinephrine- dopamine reuptake inhibitors Bupropion Headache, agitation, discontinuation syndrome*, high blood pressure in a few people, and rarely seizures Serotonin modulators (5-HT2 blockers) Mirtazapine Drowsiness and weight gain Mirtazapine does [merckmanuals.com]

  POMS measures levels of depression, anger, hostility, fatigue, and confusion, while DASS gauges other negative mood states as well, including hopelessness, lack of interest, anhedonia (lack of pleasure), agitation, irritability, and impatience with other [nutritionfacts.org]

• Difficulty Concentrating

  concentrating, remembering details, and making decisions Feelings of worthlessness, hopelessness or guilt Persistent physical symptoms such as headaches, digestive problems or chronic pain that do not respond to routine treatment Substance abuse problems [halfofus.com]

  The major symptoms of depression include the following: Feeling extremely sad, anxious, or "empty" Feeling hopeless Feeling worthless Sleeping too much or too little Loss of enjoyment from things that were once pleasurable Loss of energy Difficulty concentrating [my.clevelandclinic.org]

  It is characterized by weeks of such symptoms as low or sad mood, diminished interest in activities that used to be pleasurable, weight gain or loss, fatigue, inappropriate guilt, difficulty concentrating, and recurrent thoughts of death. [nutritionfacts.org]

  If you have depression, some symptoms you might experience include: feeling down or ‘numb’ for longer than two weeks losing interest in activities that you used to enjoy feeling like you don’t get much pleasure out of things difficulty concentrating negative [au.reachout.com]

  concentrating or making decisions Suicidal thoughts or intentions Treatments Although depressive disorder can be a devastating illness, it often responds to treatment. [nami.org]

• Sleep Disturbance

  Patients with unimpaired sleep at baseline showed greater improvements over time than those with sleep disturbances. Changes on the MCCB were not correlated with other psychometric variables. [ncbi.nlm.nih.gov]

  People who have a history of sleep disturbances, medical illness, chronic pain, anxiety and attention-deficit hyperactivity disorder (ADHD) are more likely to develop depression. [nami.org]

  Symptoms: Sadness and or irritability Loss of interest or pleasure in everyday activities Loss of appetite—or increase in appetite Sleep disturbances—either insomnia or excessive sleeping Agitation or slowing in behavior Fatigue Feelings of worthlessness [nationalmssociety.org]

  sleep disturbances, or sleeping too much Fatigue and lack of energy Difficulty thinking clearly, remembering, concentrating, or making decisions Appetite or weight changes Recurrent thoughts of death or suicide Physical symptoms such as headaches, stomachaches [psycom.net]

  disturbances, including insomnia or sleeping too much Tiredness and lack of energy, so even small tasks take extra effort Reduced appetite and weight loss or increased cravings for food and weight gain Anxiety, agitation or restlessness Slowed thinking [mayoclinic.org]

• Sexual Dysfunction

  Selective serotonin reuptake inhibitors (SSRIs) Citalopram Escitalopram Fluoxetine Fluvoxamine Paroxetine Sertraline Vilazodone Sexual dysfunction (primarily, delayed orgasm but also loss of desire and erectile dysfunction in some people), nausea, diarrhea [merckmanuals.com]

  What about sexual dysfunction related to antidepressants? The SSRI antidepressants can cause sexual dysfunction. SSRIs reportedly decrease sex drive (libido) in both men and women. [medicinenet.com]

• Female Sexual Dysfunction

  What about sexual dysfunction related to antidepressants? The SSRI antidepressants can cause sexual dysfunction. SSRIs reportedly decrease sex drive (libido) in both men and women. [medicinenet.com]

A combination of tests would help in diagnosis of depression. The following methods would be employed for diagnosing the condition:

• Physical examination: At the preliminary level, a thorough physical examination is carried out to check for presence of physical ailments if any; because many a time depression is linked to physical ailment. In addition, the psychologist would also ask various detailed questions concerning health of the individual [7] [8].
• Laboratory tests: Blood tests to detect complete blood count are required to assess the presence of underlying disease conditions such as thyroid disorders.
• Psychological examination: In this, the individual is asked in depth questions about the symptoms, thoughts and feelings. He/she are also asked to fill in a questionnaire to arrive at a definite conclusion.
• Imaging studies: CT scan and MRI scan of the brain can be considered to evaluate underlying disease conditions which are causing depression.

A combination of treatment regime has been proved to be effective for individuals with depression. The following methods are employed in treating depression:

• Medications: Antidepressants such as serotonin-specific reuptake inhibitors (SSRIs), serotonin–norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants and atypical antidepressants are used for treating depressions. Amongst these classes of drugs, antidepressants containing SSRIs are considered to be safe with fewer side effects. In addition to antidepressants, individuals may also be put on antipsychotics and mood stabilizers to enhance the effect of medications.
• Psychotherapy: This method involves interpersonal therapy, cognitive behavioral therapy and commitment therapy that helps individuals to overcome the condition through counseling [9]. 
• Electroconvulsive therapy is a process wherein electrical currents are imparted to the brain which significantly improves the levels of neurotransmitters providing immediate relief from severe depression. It is a method of choice for those individuals for whom medication and other therapies did not work.
• Transcranial magnetic stimulation is a process in which magnetic impulses are passed on to the brain which stimulates the nerves cells involved in mood regulation [10].

A high incidence of morbidity and mortality is associated with depression owing to increase in suicidal attempts amongst the depressed population. The prognosis of the condition is good with treatment as about 70 to 80% of individuals report significant reduction in symptoms of depression when given appropriate treatment. However, it has also been observed that about 50% of individuals do not respond to the initial phases of depression [5].

The exact cause of depression is not clearly understood. However interplay of various factors has been known to play a role. The following factors can cause depression:

• Brain chemical imbalance: Neurotransmitters are brain chemicals that are known to play a vital role in causation of depression. Imbalance in the level of neurotransmitters can trigger depressive symptoms.
• Physical changes: Individuals with depression are thought to have certain physical changes in the brain which again are a significant factor that can help determine the causative factor.
• Genetic factors: Certain genes are known to play foul in causation of depression as this mood disorder is thought to run in families. Individuals with family history of depression are more prone to suffer from this disorder.
• Hormones: Hormonal changes or imbalance due to certain disease conditions can cause depression.
• Life events: Individuals who have suffered the loss of loved ones, or have undergone physical or mental trauma during childhood are likely to develop depression in the future.
• Drug abuse: Use of certain medications or recreational drugs can also trigger symptoms of depression [2].

Depression is a common mood disorder affecting more than 20 million individuals in the US. The lifetime incidence of depression amongst men and women in the US has been estimated to be 12% and 20% respectively. Depression is a more common phenomenon amongst the women population [3].

It has also been reported that the incidence of depression is higher amongst the elderly population owing to advancing age and increase in prevalence of medical illness and institutionalization in this age group.

The pathophysiology of depression is not clearly understood. Certain clinical trials have pointed towards disturbance in the various neurotransmitters to be a major factor. In addition, development of vascular lesions that damages the functioning of the neural networks involved with emotional regulation play a significant role in development of depression. When the brain activity of affected individuals were studied through neuroimaging tests, it was revealed that depressed mind is associated with decreased metabolic activity in neocortical structures with an increase in metabolic activity of limbic structures [4].

Depression can seldom be prevented. However, certain steps can help avoid its onset. These include:

• Taking help of family and friends when feeling low or sad
• Considering medical intervention when first signs of depression appear
• Working out various ways to keep stress at bay

Such a type of mood disorder if not treated on time can make life worse for the individual living with it. Depression requires long term treatment and individuals generally do better with medications and psychological counseling. Affected individuals exhibit symptoms of constant feeling of sadness and lack of interest in activities [1]. Depression is also termed as major depressive disorder or clinical depression.

Definition

Depression is a type of mood disorder characterized by constant feeling of sadness accompanied by lack of interest in life. Such a type of condition can strike individuals at any age and is more prevalent amongst the female population.

Cause

Depression is thought to occur due to interplay of various factors such as genetics, unpleasant life events, hormonal imbalance and drug abuse. Individuals with certain underlying disease condition can also fall prey to depression.

Symptoms

Individuals with depression exhibit signs of sadness, lack of interest in various activities, loss of appetite or sudden increase in food cravings, lack of sleep, poor concentration, lack of energy and fatigue.

Diagnosis

Individuals who seek medical advice are asked to fill up a questionnaire containing list of questions to better understand their condition and thought process. In addition, blood tests and imaging studies will also be required to diagnose underlying disease conditions.

Treatment

Depression is best treated through combination of medication and psychotherapy. Those who fail to respond to these modes of treatment are given electroconvulsive therapy.

1. Pampallona S, Bollini P, Tibaldi G, Kupelnick B, Munizza C. Combined pharmacotherapy and psychological treatment for depression: a systematic review. Arch Gen Psychiatry. Jul 2004;61(7):714-9.
2. Richardson LP, Katzenellenbogen R. Childhood and adolescent depression: the role of primary care providers in diagnosis and treatment. CurrProblPediatrAdolesc Health Care 2005; 35:6.
3. Klerman GL. The current age of youthful melancholia.Evidence for increase in depression among adolescents and young adults. Br J Psychiatry. Jan 1988;152:4-14.
4. Kempton MJ, Salvador Z, Munafò MR, Geddes JR, Simmons A, Frangou S, et al. Structural neuroimaging studies in major depressive disorder. Meta-analysis and comparison with bipolar disorder. Arch Gen Psychiatry. Jul 2011;68(7):675-90.
5. Stewart JW, McGrath PJ, Blondeau C, et al. Combination antidepressant therapy for major depressive disorder: speed and probability of remission. J Psychiatr Res 2014; 52:7.
6. Friedman RA, Leon AC. Expanding the black box - depression, antidepressants, and the risk of suicide. N Engl J Med. Jun 7 2007;356(23):2343-6.
7. Arroll B, Khin N, Kerse N. Screening for depression in primary care with two verbally asked questions: cross sectional study. BMJ. Nov 15 2003;327(7424):1144-6
8. U.S. Preventive Services Task Force. Screening for Depression. May 2002. 
9. Mufson L, Fairbanks J. Interpersonal psychotherapy for depressed adolescents: a one-year naturalistic follow-up study. J Am Acad Child Adolesc Psychiatry. Sep 1996;35(9):1145-55. 
10. Martiny K, Lunde M, Bech P. Transcranial low voltage pulsed electromagnetic fields in patients with treatment-resistant depression. Biol Psychiatry 2010; 68:163.