DSM–5 criteria for diagnosing depression in the pediatric population:

• The presence of at least 5 of the following items in the same 2-week period with having a change in the level of function. At least 1 of the items is either depressed mood or loss of interest or pleasure. It is important to note that other medical conditions can not explain symptoms.
  • Depressed or irritable mood most of the day, almost every day, as demonstrated by either subjective report, for example, the patient feels sad, empty, or hopeless, or observation made by others, for example, the patient appears sad. 
  • A significant decrease in interest or pleasure in activities most of the day, nearly every day as indicated by self-reporting or observation
  • Failure to make expected weight gain or remarkable weight loss when not dieting or a remarkable weight gain, or decrease or increase in daily appetite
  • Lack of sleep or excessive sleeping almost every day
  • Psychomotor unrest or retardation almost every day (observable by others, not merely subjective feelings of restlessness).
  • Lack of energy nearly every day
  • Feelings of worthlessness or inappropriate guilt (possibly delusional) nearly every day (not merely self-reported or guilt for being sick)
  • Decrease capacity to think or concentrate or indecisiveness, almost every day (either by self-report or as observed by others)
  • Repeated thoughts death (not just fear of dying), recurrent suicidal ideation without specific plans; suicide attempt; or a definite plan to commit suicide

• The illness causes clinically remarkable distress or impairment in social, occupational, or other important areas of functioning.

• The episode is not due to the physiological effects of a substance or another medical condition

• The occurrence of the major depressive episode cannot be explained by schizoaffective disorder, schizophrenia, schizophreniform disorder, delusional disorder, or other specified and unspecified schizophrenia spectrum and other psychotic disorders

•  Had no manic or hypomanic episodes

The USPSTF (US Preventive Services Task Force) recommends screening for a major depressive disorder (MDD) in adolescents aged 12 to 18 years.[15] Some screening questionaries are available to screen for depression in primary settings. Examples are:

1. PHQ9: The 9-item Patient Health Questionnaire, scores each of the nine DSM criteria as "0" (not at all) to "3" (nearly every day), providing a 0 to 27 severity score
2. The Zung Self-Rating Depression Scale: A 20-item self-report questionnaire.
3. The Beck Depression Inventory-II (BDI-II): 21-item self-report inventory

There is no specific blood test or imaging that can be done to diagnose depression. However, the evaluation of depression needs to include some investigations to rule out some of the differential diagnosis. Examples are:

• Complete blood count (CBC) and vitamin B-12 levels
• Electrolytes including magnesium, calcium, and phosphate.
• TSH, T3, free T4
• Liver function tests, renal function test (blood urea nitrogen, creatinine)

Other investigations should be ordered whenever other medical illnesses are suspected, for example, urine toxicology screen, blood alcohol level, HIV test, dexamethasone suppression test, and ACTH stimulation test.

Treatment should aim for recovery, achieving full remission of symptoms, and returning to the premorbid level of functioning. Biopsychosocial treatment plans for children and adolescent is similar to adults' plans. However, in children and adolescents, clinicians often start with psychosocial interventions.

Psychosocial Interventions Involving the Child and Parents

Psychosocial interventions are the first-line treatment in case of mild-to-moderate depression.

1. Psycho-education including education about the illness, the importance of having a good sleep and good nutrition
2. Exercising for at least 30 minutes a day
3. Cognitive and behavioral therapy to help the depressed individual identify cognitive distortions and to learn cognitive restructuring skills, problem-solving skills and to use behavioral activation techniques
4. Interpersonal therapy aimed to decrease interpersonal conflicts by helping depressed individual learning interpersonal problem-solving skills and changing dysfunctional communication and relational patterns
5. Family therapy: Different family therapy modules could be of help to the depressed individual and family.

Medication

Different studies had shown that antidepressants efficacy is different between adults and children. The placebo effect is stronger among children and adolescents compared to adults, especially with mild-moderate depression.

It is important to discuss the effects and side-effects with the patient and parents. Typically, for the first month after prescribing an antidepressant follow-up should be weekly. This allows for close monitoring of side effects as well as supportive management.

Antidepressants that are most commonly used in this age group are fluoxetine, sertraline, citalopram, and escitalopram. Fluoxetine and escitalopram are approved by the FDA for adolescent depression. Venlafaxine, a serotonin-norepinephrine repute inhibitor (SNRI), is a second-line drug due to its side effects.

Side Effects

One of the major side effects of antidepressants is an increase in suicidal thoughts, but not suicidal attempts. Thus, monitoring suicidal risk is required. Other side effects include gastrointestinal problems, agitation, nightmares and sleep disturbance, weight gain, and sexual dysfunction.

Management of Comorbid Disorders

Clinicians should monitor comorbid disorders such as sleep disorders, anxiety disorders, and other underlying medical causes of depression.

Bipolar Depression

To diagnose a bipolar affective disorder, clinicians need to document one manic or hypomanic episode. The challenge with the pediatric population is that bipolar disorders often start with an episode of depression in childhood or adolescence.

Adjustment Disorder

The onset of symptoms in adjustment disorder occurs following a significant life event.

Substance Use Disorders

Either withdrawal from substances, for example, amphetamines or cocaine, or intoxication (alcohol) could present with a clinical picture similar to depression. Depression could be diagnosed as a concurrent disorder if depressive symptoms persist or precede the onset of substance use.

Medical Conditions

Different medical conditions could present with depression, for example, multiple sclerosis, stroke, or hypothyroidism.

Attention-Deficit Hyperactivity Disorder

Attention-deficit hyperactivity disorder (ADHD) could present with irritable mood, poor concentration, and these symptoms are similar in pediatric depression symptoms.

The most important factor in predicting the severity and improvement percentage of depression is the duration of untreated depression. Active treatment decreases the depressive episode duration.[16] Remission rate depends on different factors like disorder severity, with rates among people with severe disorders being 20% to 30% lower than mild-to-moderate depression. Around, 60 % to 90% of mild-to-moderate depressive episodes in adolescents remit within a year. However, recurrence within 5 years occurs in around 50 % to 70%. Patients with major depression from specialist psychiatry settings have had long-term recurrence rates of between 50% and 64%.[17] Relapse rate is higher when the remission from depression is partial (67.6%) compared to when it is complete remission (15.18%).[18] Children and adolescents who develop a recurrent or chronic disorder extending into adulthood are more likely to suffer considerable disability and impairment.[19]

Major depressive disorder in the pediatric population is a treatable condition. However, it is mostly underdiagnosed and under-treated. The goal of treatment should be to minimize the impact of depression on the child's functioning at home, school and on the social/peer relationships while aiming for a full recovery. This would be better obtained via outpatient treatment with an interprofessional team consisting of a mental health nurse, a psychiatrist, a pediatrician, a psychotherapist, and a case manager. Admission to the inpatient unit should be considered when the depression is severe, or the child's safety cannot be guaranteed. Pediatricians and mental health professionals should always promote and advocate for this population's mental health, increase awareness and aim for decreasing the stigma.[20]