One confound that could be overlooked when it comes to attachment style and well being later in life is socioeconomic status of the parents. This would greatly influence how they interacted with their child. Perhaps people in a middle class family have to work together to keep the family going, but are not so overworked that the family dynamic becomes stressful. Therefore those families may develop closer bonds. This could help the children be better off later in life. Whereas children that come from poverty may have stressful family dynamics due to money problems. Children in poverty often repeat the cycle and as adults may be worse off than those who did not start out in poverty. Attachment style may not be the influential factor, but rather the money.
I agree that people with a higher socioeconomic status are generally more stable in lifestyle as far as housing, food, and ecomonic well being goes. However, it does not indicate that the interpersonal relationships in a child's life are stable, and that can have a great impact on their ability to form normal, healthy relationships later in life. No amount of money or education can make a person capable of trusting and intimate relationships.
