Demographic, psychopathological and clinical characteristics of study participants
| Characteristic | Patients, mean ± SD* n = 29† | Healthy controls, mean ± SD* n = 20 | Statistical test‡ | p value |
|---|---|---|---|---|
| Age, yr | 27.7 ± 7.2 | 30.6 ± 6.6 | t47 = 1.45 | 0.15 |
| Sex, female:male | 7:22 | 6:14 | χ21 = 0.21 | 0.65 |
| Education, yr | 11.4 ± 2.8 | 14.2 ± 2.5 | U = 101.5 | ≤ 0.001 |
| Smoking, pack-years | 5.7 ± 13.7 | 2.4 ± 4.8 | U = 239.5 | 0.25 |
| Duration of illness, yr | 7.2 ± 7.1 | — | — | — |
| Age of onset, yr | 21.0 ± 4.8 | — | — | — |
| Chlorpromazine equivalents, mg/d | 497.7 ± 407.4 | — | — | — |
| BNSS score | ||||
| Apathy (motivation and pleasure) | 15.5 ± 6.9 | — | — | — |
| Diminished expression | 8.6 ± 7.0 | — | — | — |
| SANS score§ | ||||
| Apathy | 11.9 ± 5.6 | — | — | — |
| Diminished expression | 10.4 ± 9.6 | — | — | — |
| PANSS score¶ | ||||
| Positive | 6.4 ± 2.5 | — | — | — |
| Negative | 12.0 ± 5.2 | — | — | — |
| Disorganized | 4.7 ± 2.0 | — | — | — |
| Excited | 4.5 ± 0.7 | — | — | — |
| Depressed | 5.4 ± 2.4 | — | — | — |
| Total | 47.7 ± 10.2 | — | — | — |
| CDSS total score | 2.1 ± 2.5 | — | — | — |
| GAF score | 58.1 ± 9.6 | — | — | — |
| PSP total score | 58.2 ± 9.1 | — | — | — |
| Cognition (composite cognitive ability)** | −0.85 ± 0.80 | 0 ± 0.58 | t47 = 4.07 | ≤ 0.001 |
| MWT IQ | 24.5 ± 6.0 | 28.7 ± 2.8 | t47 = 2.89 | 0.006 |
BNSS = Brief Negative Symptom Scale; CDSS = Calgary Depression Scale for Schizophrenia; GAF = Global Assessment of Functioning; MWT IQ = Multiple Word Test Intelligence Quotient; PANSS = Positive and Negative Syndrome Scale; PSP = Personal and Social Performance scale; SANS = Scale for the Assessment of Negative Symptoms; SD = standard deviation.
↵* Unless otherwise indicated.
↵† All patients were receiving atypical antipsychotics at the time of testing.
↵‡ We investigated potential group differences using 2-sample t tests for continuous data and χ2 tests for categorical data. For data with non-normal distribution, we applied Mann–Whitney U tests.
↵§ Apathy includes avolition/apathy and anhedonia/asociality; diminished expression includes affective flattening or blunting and alogia.
↵¶ Positive factor = P1, P3, P5, P9; negative factor = N1, N2, N3, N4, N6, G7; disorganized factor = P2, G5, N11; excited factor = P4, P7, G8, G14; depressed factor = G2, G3, G6.
↵** Cognition data have been z-transformed based on the data of the control group for each test separately. The composite cognitive ability score was computed as the mean of the z-transformed test scores at the participant level.