Children should have at least five symptoms for a period of two weeks including either the first or the second one to be diagnosed with major depressive disorder:

• Feeling or appearing depressed, sad, tearful, or irritable.
• Not enjoying things as much as they used to.
• Changes in appetite and/or weight.
• Sleeping more or less than usual.
• Feeling tired or having less energy.
• Feeling like everything is their fault or not being good at anything.
• Having more trouble concentrating.
• Psychomotor retardation or agitation.
• Having thoughts of suicide or wanting to die.

There are also some secondary symptoms:

• Caring less about school or not doing well at school.
• School refusal.
• Spending less time with friends or in after-school activities.
• Somatic complaints in general.

Physical complaints (e.g. headaches; stomach aches) are more common in children. Substance use (e.g. alcohol; drugs) is more common in adolescence. The prevalence of major depressive disorder is 2.8% in school-age children (i.e. 6-12 years) and 5-6% in adolescents (i.e. 13-18 years). However, compared to adults, children and adolescents are still underdiagnosed and undertreated. 

The general guideline for mild to moderate depression is psychosocial treatment. For severe depression, the guideline is a combination of psychosocial treatments and medication. However, one should be cautious with using medication with children and adolescents as there is an increased suicide risk with medication use. This may be because the medication increases impulsiveness. It should always be used in the context of extensive case conceptualization and in consultancy with a psychiatrist.

Beck’s cognitive theory of depression states that depression is the result of negative cognitions. There are automatic negative interpretations of ambiguous situation and cognitive errors (e.g. “bad things happen because of me”). This leads to negative schemes (e.g. “I am unlovable) which leads to depression. The negative beliefs are activated when faced with stressful circumstances and this interferes with coping and positive mood. There is black and white thinking, selective observation, overgeneralization and personalization of negative events (i.e. personal attribution). Depressogenic thinking is resistant to disconfirmation, partially due to the enduring styles of information processing that promote belief maintenance (e.g. focus on negative information).

The cognitive vulnerability model states that individuals at risk for depression selectively focus on and have better memory recall for negative rather than positive stimuli. A behavioural approach to depression holds that depression results from low levels of positive reinforcement and high levels of punishment and aversive control. This leads people to withdraw from negative interactions and avoid situations that may produce low positive reinforcement which, eventually, leads to a depressive cycle.

Theory is necessary because explaining the rationale behind a treatment makes it more understandable for a client and improves treatment adherence. The client needs to view the treatment as useful and needs to understand why

Cognitive-behavioural therapy (CBT) and interpersonal therapy (IPT) are two effective treatments and are in the guidelines. The format is being adapted for different contexts (e.g. individual; group; family) and from preventative to curative, from face-to-face to online. Most of the manuals for these treatments are for older children and adolescents although there are some for younger children.

The treatment manuals have different characteristics:

• It includes the theoretical orientation.
• It includes the rationale.
• It includes the guidelines for therapists.
• It includes information on the sessions and activities.
• It specifies the population.

The major idea is that training and learning is possible using a manual. There are separate therapist and client workbooks. The skills are practiced and the therapist is viewed as a coach. Treatment typically concludes with relapse prevention.

CBT typically begins with psychoeducation and the theory of the intervention. There is also an early application of behavioural techniques. Afterwards, cognitive restructuring is used. The believed mechanisms of treatment effects for CBT are involvement in negative cognitive style and behavioural mood regulation skills. CBT combines cognitive and behavioural strategies. It includes focus on specific and current actions and cognitions (1), structured sessions (2), repeated skills practice (3), use of rewards and contracts (4), homework assignments (5) and a relatively small number of sessions (6). It tries to teach youth coping styles to counteract the diverse factors that contribute to their depression.

There are some general principles of CBT:

1. Monitoring depressive mood (e.g. mood diary)
   This is done by providing psychoeducation. The rationale is to recognize depressive feelings. The goal is to teach children how to correctly recognize emotion and when to use skills to tackle them. Recognizing emotions will also allow children to use coping skills when they feel that way. Lastly, monitoring mood will also show them that they do not always feel depressed.
2. Challenge and transform negative cognitions
   This requires tracing and recognizing thoughts, which can be done through cartoons (1), questionnaires (2), interpreting ambiguous situations (3) and doing event-thought-feelings-behaviour schemas (4). People need to challenge their negative thoughts (i.e. counterthought) by thinking of alternative and positive interpretations of situations. Challenging negative thoughts could be done by using a pie chart (i.e. asking someone: “what would others say when they got a bad grade?”). The client then needs to give percentages to other explanations (e.g. how many percent of the people would use this reason) to see the irrationality of extremely negative thoughts.
3. Address behavioural symptoms of inactivity (i.e. behavioural activation)
   This is done by reviewing the level of activities (1), monitor activities (2), choose fun activities (3) and plan activities (4). Afterwards, activities are monitored again and mood is also monitored. The rationale is linking mood and being active. It includes rewarding people for appropriate behaviour.

The main idea is that there is an activating event (e.g. no one talked to you during school break) and this is automatically associated with a negative thought (e.g. no one likes me). This negative thought then leads to a depressed feeling. In CBT, people are taught to use counterthoughts and this leads to a new, non-depressed feeling. Goal-setting is important for the client as this makes the treatment concrete.

Returning to a social setting (e.g. school) requires social problem solving (e.g. “how do I explain that I was gone for months?”). This is done by learning social skills and troubleshooting. It is usually related to problems caused by isolation due to depressive mood.

There are several factors which may influence the treatment outcome in CBT:

• Hopelessness
  Lower levels of hopelessness are associated with better responses to CBT but the moderating effect was not maintained in the long-term.
• Positive problem-solving skills and mindsets
  This allows people to make better use of CBT.
• Coping style
  This is a moderator of the effects of CBT with more positive coping styles leading to better outcomes.
• Household conflict
  CBT has a worse outcome for males compared to another treatment in a high-conflict household and the same holds for females in a low-conflict household.
• Marital conflict
  This moderates the response to CBT for highly oppositional adolescents.
• Family function
  A good family function is associated with more benefit from combined treatment.
• Stressful life events and substance use
  CBT is superior for people with low or moderate levels of stressful life events and substance use but not for those with high levels.
• Income
  There is an equal effectiveness of combination treatment and medication and both are better to CBT in low-income families.
• Ethnicity
  There are stronger effects for combined treatment for Caucasian adolescents.
• Comorbidity
  Comorbid ADHD leads to better outcomes with combination therapy and the same may be the case for anxious youth.
• Trauma history
  This moderates the response to flatten out the superior effects of combination therapy for youth with a history of sexual abuse. It reverses the benefits of combination and monotherapy for youth with a history of physical abuse.

Adolescent coping with depression course (CWD-A) is a group-based CBT intervention for depression and consists of 16 two-hour sessions over 8 weeks. People who received this in usual care did not improve compared to usual care. CBT may have a strong clinical impact in four ways:

1. Focus on prevention rather than treatment
   CBT can be a method of prevention of depression for at-risk youth as pharmacological intervention are not recommended for prevention.
2. Use CBT to augment medication treatment
   CBT may build on the symptom response or remission which is the result of anti-depressants.
3. Embed CBT within standard medical care
   This may be cost-effective and practical to reduce depression rates.
4. Use eMental health approaches
   CBT may target youth who do not actively seek treatment by making it online.

The interpersonal therapy (IPT) by Mufson holds that depression emerges from interpersonal conflicts and flaws. This therapy is believed to help adolescents develop more rewarding relationships. The main aims are to recognize how feelings and interpersonal problems affect mood (1), increase communication and problem-solving skills (2) and decrease depressive symptoms (3).

IPT is especially effective when adolescents have significant interpersonal problems (1), experience high levels of mother-child conflict (2) and have problems with peer relationships (3).

33% of children and young people with anxiety or depression show improvement in treatment as usual conditions. There is a 60% likelihood that a randomly selected youth receiving psychotherapy would be better off than a control condition. However, less than 10% of all interventions not involving a professional have been scientifically researched. This means that depression research for youth is insufficiently studied.

The effects of therapy for depression are modest but there is no real change over the past 13 years. In general, there is a moderate overall effect size for active therapy versus control therapy. There are several moderators:

• The effects were larger for IPT than for CBT.
• The effects were larger for youth self-report than fir parent-report.
• The effects were larger for comparisons with waitlists than compared to active controls.