Table 1

Sample demographic characteristics*

CharacteristicMZ (n = 159)DZ (n = 98)Twin 1 (n = 132)Twin 2 (n = 131)
Mental well-being100.0 ± 10.299.5 ± 10.1100.5 ± 9.999.3 ± 10.7
Depression/anxiety symptoms10.4 ± 10.811.7 ± 10.710.4 ± 10.611.1 ± 10.7
Early-life stress events1.7 ± 1.71.4 ± 1.41.6 ± 1.71.6 ± 1.6
Premature birth or other birth complications47%44%45%47%
Adoption0%0%0%0%
Major surgery or repeated hospitalization11%15%12%14%
Life-threatening illness or injury10%8%11%8%
Sustained bullying17%15%13%20%
Physical abuse5%3%5%4%
Sexual abuse5%6%7%4%
Emotional abuse9%10%10%8%
Poverty or neglect2%0%1%2%
Natural disaster4%0%2%4%
House destroyed by fire or other means1%0%0%1%
Witness of warfare0%0%0%0%
Parents divorced or separated10%5%9%8%
Long period of separation from immediate family7%4%7%5%
Sustained family conflict12%13%14%11%
Death of immediate family3%3%4%3%
Life-threatening illness in immediate family6%7%8%7%
Witness domestic violence in family12%5%8%10%
Witness or experience some other traumatic event6%5%6%5%
  • DZ = dizygotic; MZ = monozygotic.

  • * Results presented as mean ± standard deviation, or as frequency (%).

  • No significant differences between groups for well-being, depression and anxiety scores, or average early-life events.