Table 1.
Demographic and clinical characteristics of twins meeting definite or probable DSM-5 criteria for lifetime history of MD (MD Affected) versus no lifetime history of MD (MD Unaffected).
| M (SD) or n (%) | ||||
|---|---|---|---|---|
| MD unaffected n = 111 | MD affected n = 39 | t/χ2 | P | |
| Demographic/Sample | ||||
| Age, years | 17.49 (1.3) | 17.60 (1.3) | 0.66 | 0.51 |
| Sex, female | 81 (73.0%) | 29 (74.4%) | 0.28 | 0.87 |
| thnicity, Hispanic | 5 (4.5%) | 3 (7.7%) | 0.58 | 0.43 |
| Nicotine usea, current smoker | 2 (1.8%) | 3 (7.7%) | 3.11 | 0.11 |
| Clinical characteristics | ||||
| SMFQ | 4.4 (3.7) | 9.0 (6.0) | 6.40 | <0.001 |
| History of psychotropic medication use | 2 (1.8%) | 4 (10.3%) | 0.64 | 0.62 |
| Panic attackb | 10 (9.0%) | 6 (15.4%) | 1.19 | 0.28 |
| Social anxiety disorder | 10 (9.1%) | 8 (20.5%) | 3.54 | 0.08 |
| Specific phobia | 8 (7.3%) | 7 (17.9%) | 3.63 | 0.07 |
| Generalized anxiety disorder | 2 (1.8%) | 4 (10.3%) | 5.31 | 0.04 |
| MD features | ||||
| Age of onset (years) | – | 14.9 (1.7) | ||
| Number of major depressive episodes, n | ||||
| 1 episode | – | 17 (43.6%) | ||
| 2–3 episodes | – | 16 (41.0%) | ||
| 4–5 episodes | – | 3 (7.7%) | ||
| ≥6 episodes | – | 3 (7.7%) | ||
| Time since last MDE (years) | – | 1.31 (1.7) | ||
| Number of symptoms during worst MDE | – | 5.69 (1.1) | ||
SMFQ Short Mood and Feelings Questionnaire.
aFor smokers, Fagerstrom test for nicotine dependence scores ranged 2 (low dependence) to 6 (moderate dependence) with a Mode = 2, Median = 2, and Mean = 3.
bNo case meet full criteria for panic disorder.