1. Depressive Disorders Chapter 17
Daniel N. Klein, Autumn J. Kujawa, Sarah R. Black, and Allison T. Pennock

2. HISTORICAL CONTEXT
Recognition of child and adolescent depressive disorders did not emerge until the late 1970s.
Before the 1970s depression was thought to be rare in children and clinicians believed that depression was expressed in behavioral disturbances such as behavior problems, enuresis, and somatic concerns.
During the late 1970s, investigators demonstrated that many children and adolescents met full adult criteria for major depressive disorder (MDD).

3. TERMINOLOGICAL AND CONCEPTUAL ISSUES
Depression is a complex phenomenon and can encompass:
A mood state
A clinical syndrome that can be caused by a variety of nonpsychiatric factors such as neuroendocrine disorders and psychoactive drug use
A psychiatric disorder
Depressive disorders are multifactorial conditions—caused by combinations of many etiological factors.
Depressive disorders are probably etiologically heterogeneous, meaning that there are different subtypes of depression that are caused by different sets of etiological processes.
Depressive disorders are characterized by both equifinality and multifinality.

4. DIAGNOSIS AND CLASSIFICATION
DSM-IV (2000)
MDD: A period of persisting depressed or irritable mood or loss of interest or pleasure that lasts at least 2 weeks and is accompanied by a variety of other symptoms, including:
Low energy and fatigue
Inappropriate feelings of guilt or worthlessness
Difficulty thinking, concentrating or making decisions
Sleep disturbance (insomnia or hypersomia)
Appetite disturbance (eating too little or too much or significant weight loss or gain)
Psychomotor disturbance (either retardation [extreme slowing in movement and speech], or agitation [extreme restlessness])
Thoughts of death or suicidal thoughts or behavior.

5. DIAGNOSIS AND CLASSIFICATION
Dysthymic disorder (DD) is a milder but more chronic condition, characterized by a period of depressed or irritable mood that is present for at least half the time for at least one year and is accompanied by several other depressive symptoms.
Subtypes
Unipolar-bipolar distinction, differential symptom presentation, and course.
Unfortunately, subtyping has largely been ignored in child and adolescent depression.

6. DIAGNOSIS AND CLASSIFICATION
Depression in Very Young Children
Little research exists on depression in infants and preschool aged children
Luby and colleagues (2003) reported that MDD can be identified in preschool-age children using modified DSM-IV criteria with a shorter duration requirement.
Preschoolers meeting modified criteria for MDD had an 11-fold greater risk of exhibiting MDD 12 to 24 months later compared to healthy children (Luby, Si, Belden, Tandon & Spitznagel, 2009).

7. EPIDEMIOLOGY Prevalence
Studies of community samples indicate that depression is rare in early childhood, increases somewhat in middle/late childhood, and rises sharply in adolescence.
A meta-analysis of 26 studies estimated that the point prevalence of MDD was 2.8% in school-age children and 5.7% in adolescents (Costello, Erkani, & Angold, 2006).
By mid-late adolescence, the lifetime prevalence of depression approaches adult rates (Rudolph, 2009).

8. EPIDEMIOLOGY Sex Differences Comorbidity
Depressive symptoms and diagnoses in males and females are similar in childhood but between the ages of 12 and 15 rates among females increase markedly (Hyde, Mezulis, & Abramson, 2008; Nolen-Hoeksema & Hilt, 2009).
Comorbidity
Depressed children and adolescents are:
8.2 times more likely than nondepressed youths to meet criteria for an anxiety disorder
6.6 times more likely to meet criteria for conduct disorder
5.5 times more likely to meet criteria for attention-deficit/hyperactivity disorder (Angold, Costello, & Erkanli,1999).

9. Course and Outcome
Clinical samples tend to have a longer duration than community samples:
Mean duration of MDD episodes is approximately 7 to 8 months.
Episodes of DD last an average of 48 months.
40% to 70% of adolescents with MDD experience a recurrence in adulthood (Fombonne et al., 2001).
Predictors of increased risk of recurrence:
Greater severity
Psychotic symptoms
Suicidality
Prior history of recurrent MDD
Subthreshold symptoms after recovery
Depressotypic cognitions
Recent stressful life events
Adverse family environments
Family history of MDD

10. RISK FACTORS Genetics Temperament Maladaptive parenting and abuse
Biological factors
Cognitive factors
Peer relationships
Life stress

11. Protective Factors
Little research on protective factors in youth depression.
Most research focuses on variables that appear to be the absence or opposite of established risk factors, such as high self-esteem and self-efficacy, an “easy” temperament, and family and peer support.

12. Conclusions and Future Directions
Genetic factors play a role in youth depression, but the strength of their influence varies as a function of development, given that genetic effects increase with age.
Genetic influences are likely to operate through intermediate phenotypes such as temperament and susceptibility to stress.
Genetic influences are also mediated and/or moderated by a number of other risk factors.
Two major sets of distal causes include genetic susceptibilities and early adversities.