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Table 1 Comparison of plasma amino acids levels and nitric oxide levels in the 9 symptoms of major depressive disorder according to the DSM-IV

From: Decreased plasma neuroactive amino acids and increased nitric oxide levels in melancholic major depressive disorder

Symptom items

Subgrouping

Asp

Glu

Gly

GABA

NO

Item 1: depressed mood

No: n = 0

Yes: n = 27

Item 2: diminished interest

No: n = 3

0.643

0.841

0.700

0.076

0.817

Yes: n = 24

Item 3: weight loss

No: n = 13

0.382

0.898

0.438

0.645

0.382

Weight gain: n = 0

Weight loss: n = 14

Item 4: disordered psychomotor state

No change: n = 4

0.417

0.450

0.883

0.985

0.346

Agitation: n = 10

Retardation: n = 13

Item 5: disordered sleep

No: n = 1

0.847

0.616

0.773

0.312

0.211

Hypersomnia: n = 2

Insomnia: n = 24

Item 6: fatigue or loss of energy

No: n = 9

0.382

0.647

0.643

0.396

0.607

Yes: n = 18

Item 7: feeling of worthlessness or guilt

No: n = 11

0.374

0.775

0.402

0.711

0.693

Yes: n = 16

Item 8: diminished ability to think or concentrate, or indecisiveness

No: n = 9

0.837

0.617

0.719

0.662

0.090

Yes: n = 18

Item 9: thought of death or suicide

No: n = 12

0.118

0.504

0.495

0.054

0.558

Yes: n = 15

  1. Notes: Comparison of plasma levels of the 4 amino acids or NO levels among different sub-phenotype groups, based upon the 9 symptoms of major depressive disorder according to the DSM-IV. No: without this symptom; Yes: with this symptom. The numbers in the Table are P values. Comparison among 3 subgroups was performed by Kruskal -Wallis H test. Comparison between 2 subgroups was performed by Mann-Whitney U test. Asp: aspartic acid; Glu: glutamic acid; Gly: glycine; GABA: gamma-aminobutyric acid; NO: nitric oxide. The 9 symptoms includes: 1. depressed mood most of the day, nearly every day, as indicated by either subjective report (e.g. feels sad or empty) or observation made by others (e.g. appears tearful); 2. markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day (as indicated by either subjects account or observation made by others); 3. significant weight loss when not dieting or weight gain (e.g. a change of more than 5% of body weight in a month), or decrease or increase in appetite nearly every day; 4. psychomotor agitation or retardation nearly every day (observable by others, not merely subjective feelings of restless or being showed down); 5. insomnia or hypersomnia nearly every day; 6. fatigue or loss of energy nearly every day; 7. feelings of worthlessness or excessive or inappropriate guilt (which may be delusional) near every day (not merely self-reproach or guilt about being sick); 8. diminished ability to think or concentrate, or indecisiveness, nearly every day (either by subjective account or as observed by others); 9. recurrent thoughts of death (not just fear of dying), recurrent suicidal ideation without a specific plan, or a suicide attempt or a specific plan for committing suicide.