The possible role of the kynurenine pathway in adolescent depression with melancholic features.

BACKGROUND: Although adolescent major depressive disorder (MDD) is acknowledged to be a heterogeneous disorder, no studies have reported on biological correlates of its clinical subgroups. This study addresses this issue by examining whether adolescent MDD with and without melancholic features (M-MDD and NonM-MDD) have distinct biological features in the kynurenine pathway (KP). The KP is initiated by pro-inflammatory cytokines via induction of the enzyme indoleamine 2,3-dioxygenase (IDO), which degrades tryptophan (TRP) into kynurenine (KYN). KYN is further metabolized into neurotoxins linked to neuronal dysfunction in MDD. Hypotheses were that, compared to healthy controls and to NonM-MDD adolescents, adolescents with M-MDD would exhibit: (i) increased activation of the KP [i.e., increased KYN and KYN/TRP (reflecting IDO activity)]; (ii) greater neurotoxic loads [i.e., increased 3-hydroxyanthranilic acid (3-HAA, neurotoxin) and 3-HAA/KYN (reflecting production of neurotoxins)]; and (iii) decreased TRP. We also examined relationships between severity of MDD and KP metabolites. METHODS: Subjects were 20 adolescents with M-MDD, 30 adolescents with NonM-MDD, and 22 healthy adolescents. MDD episode duration had to be >or= 6 weeks and Children's Depression Rating Scale-Revised (CDRS-R) scores were >or= 36. Blood samples were collected at AM after an overnight fast and analyzed using high-performance liquid chromatography. Group contrasts relied on analysis of covariance based on ranks, adjusted for age, gender, and CDRS-R scores. Analyses were repeated excluding medicated patients. Fisher's protected least significant difference was used for multiple comparisons. RESULTS: As hypothesized, KYN/TRP ratios were elevated and TRP concentrations were reduced in adolescents with M-MDD compared to NonM-MDD adolescents (p = .001 and .006, respectively) and to healthy controls (p = .008 and .022, respectively). These findings remained significant when medicated patients were excluded from the analyses. Significant correlations were obtained exclusively in the M-MDD group between KYN and 3-HAA/KYN and CDRS-R. CONCLUSIONS: Findings support the notion that adolescent M-MDD may represent a biologically distinct clinical syndrome.

The Treatment for Adolescents With Depression Study (TADS): outcomes over 1 year of naturalistic follow-up.

OBJECTIVE: The Treatment for Adolescents With Depression Study (TADS) evaluates the effectiveness of fluoxetine, cognitive-behavioral therapy (CBT), and their combination in adolescents with major depressive disorder. The authors report effectiveness outcomes across a 1-year naturalistic follow-up period. METHOD: The randomized, controlled trial was conducted in 13 academic and community sites in the United States. Stages I, II, and III consisted of 12, 6, and 18 weeks of acute, consolidation, and continuation treatment, respectively. Following discontinuation of TADS treatments at the end of stage III, stage IV consisted of 1 year of naturalistic follow-up. The participants were 327 subjects between the ages of 12 and 17 with a primary DSM-IV diagnosis of major depressive disorder. No TADS treatment was provided during the follow-up period; treatment was available in the community. The primary dependent measures, rated by an independent evaluator blind to treatment status, were the total score on the Children's Depression Rating Scale-Revised and the rate of response, defined as a rating of much or very much improved on the Clinical Global Impressions improvement measure. RESULTS: Sixty-six percent of the eligible subjects participated in at least one stage IV assessment. The benefits seen at the end of active treatment (week 36) persisted during follow-up on all measures of depression and suicidality. CONCLUSIONS: In contrast to earlier reports on short-term treatments, in which worsening after treatment is the rule, the longer treatment in the TADS was associated with persistent benefits over 1 year of naturalistic follow-up.

Immune system dysregulation in adolescent major depressive disorder.

BACKGROUND: A large body of evidence suggests that immune system dysregulation is associated with Major Depressive Disorder (MDD) in adults. This study extends this work to adolescent MDD to examine the hypotheses of immune system dysregulation in adolescents with MDD, as manifested by significantly: (i) elevated plasma levels of cytokines (interferon [IFN]-gamma, tumor necrosis factor-alpha, interleukin [IL]-6, IL-1beta, and IL-4); and (ii) Th1/Th2 cytokine imbalance shifted toward Th1 as indexed by increased IFN-gamma/IL-4. METHOD: Thirty adolescents with MDD (19 females; 13 medication-free/naïve; ages 12-19) of at least 6 weeks duration and a minimum severity score of 40 on the Children's Depression Rating Scale-Revised, and 15 healthy comparisons (8 females), group-matched for age, were enrolled. Plasma cytokines were examined using enzyme-linked immunosorbent assay. Mann-Whitney test was used to compare subjects with MDD and controls. RESULTS: Adolescents with MDD had significantly elevated plasma IFN-gamma levels (3.38+/-11.8 pg/ml versus 0.37+/-0.64 pg/ml; p<0.003), and IFN-gamma/IL-4 ratio (16.6+/-56.5 versus 1.76+/-2.28; p=0.007). A trend for IL-6 to be elevated in the MDD group was also observed (1.52+/-2.88 pg/ml versus 0.49+/-0.90 pg/ml; p=0.09). Importantly, findings remained evident when medicated subjects were excluded. CONCLUSIONS: Findings suggest that immune system dysregulation may be associated with adolescent MDD, with an imbalance of Th1/Th2 shifted toward Th1, as documented in adult MDD. Larger studies with medication-free adolescents should follow.