Table 1.
Timing of the Assessments and Response Rates for the Two Cohorts Used in the Current Study; The Health and Lifestyle Questionnaire (HLQ) Provided Data on Personal (PLE) and network (NLE) Stressful Life Events (SLE), The SSAGA Interview Instrument Assessed Depression
| Older cohort Born <1964 | Younger cohort Born 1964-1971 | Combined | |
|---|---|---|---|
| HLQ | |||
| Mailed in Years | 1988-1989 | 1989-1990 | |
| N mailed (all these individuals were complete pairs) | 7616 | 8538 | 16154 |
| N of eligible participants | 7338a | 6502b | 13840 |
| N received (% responders, % female) | 6329 (86d, 65) | 5060 (78d, 57) | 11389 (82, 61) |
| Mean age (SD; range) | 42.3 (14.1; 24-95) | 23.4 (2.3; 18-29) | 32.3 (13.6; 18-95) |
| % with 1+ PLEs | 54 M, 53 F | 67 M, 67 F | 59 M, 58 F |
| % with 1+ NLEs | 63 M, 68 F | 61 M, 64 F | 62 M, 67 F |
| SSAGA | |||
| Telephoned in Years | 1992-1994 | 1996-2000 | |
| Mean Interval, HLQ to SSAGA (SD; range) | 3.9 (0.5; 1.1-5.0) | 6.7 (1.4; 3.8-10.0) | 4.2 (1.0; 1.1-10.0) |
| N telephoned (all these individuals were complete pairs) | 7764e | 8538 | 16302 |
| N of eligible participants | 7321f | 7325g | 14646 |
| N participating in depression section (% responders, % F) | 5992 (82, 65) | 6226 (85, 55) | 12190 (83, 60) |
| Mean age (SD; range) | 46.1 (14.2; 28-99) | 30.3 (2.4; 24-37) | 37.8 (12.7; 24-99) |
| % with Lifetime Major Depression (MD)h, i | 16 M, 18 F | 15 M, 22 F | 15 M, 20 F |
Note:
139 twin pairs were excluded, as one or both twins had died since participation in 1981.
18 pairs were in the older cohort so were excluded from the younger cohort, attempts were made to locate all non-responders but despite extensive effort 1000 pairs could not be recontacted - understandable, as we had recruited the majority of this cohort some 10 years earlier when they were at school.
c Includes participants who had failed to return a completed questionnaire but were followed up by telephone (up to five times), and asked to then complete an abbreviated telephone interview to obtain basic demographic information.
Response rate was higher for the older cohort as they were a sample of known responders; each had responded to a mail survey in 1981.
Includes the 3808 twin pairs from the HLQ plus 74 additional pairs.
443 individuals were ineligible for the study as they either; could not be located (87 individuals), were overseas (59 individuals), were deceased (295 individuals), or were not assigned for interview by the end of the study (2 individuals).
1213 were ineligible for the study as 268 pairs were lost and 677 individuals either; could not be located, were deceased, were incapacitated, were otherwise unable to complete the interview, or were not assigned for interview by the end of the study.
For a conservative diagnosis of DSM-IV MD, cases with postpartum onset are removed. Hence, the MD rate for females in the older cohort is lower than that in previous reports of this cohort (Bierut et al, 1999; Gillespie et al, 2005).
The MD diagnoses reported in this table includes cases with first onsets occurring before (as well as after) the reporting of SLE.