First espoused by Bowen (1976, 1978), family systems theory provides a developmental paradigm that focuses on how an individual's sense of self emerges in the context of emotional attachments in his or her multigenerational family system. Differentiating from one's family of origin, the cornerstone of Bowen's theory, is a key developmental task associated with young adulthood (Carter & McGoldrick, 1989). Differentiation of self refers to an individual's ability to function in an autonomous and self directed manner without being controlled by family members or significant others and without emotionally cutting oneself off from these significant relationships (Bowen, 1978; Kerr & Bowen, 1988). In other words, differentiated individuals are able to separate themselves from unresolved emotional attachments in their families without severing significant relationships. Undifferentiated individuals, on the other hand, tend to remain fused in relationships with parents and significant peers and/or emotionally cut off from these relationships (Johnson & Waldo, 1998; Kerr & Bowen, 1988). Fused relationships are characterized by enmeshment and emotional reactivity, whereas emotional cutoffs are characterized by reactive disengagement (Johnson & Waldo, 1998).
A central barometer of differentiation is an individual's ability to separate thoughts and feelings (Bowen, 1978). Differentiated individuals are not overwhelmed by emotionality at the expense of their intellect, whereas Undifferentiated individuals are ruled by their emotions. Differentiated individuals are inner-directed and readily take an "I position" rather than act reactively in response to external events and others' emotionality (Kerr & Bowen, 1988; Skowron & Friedlander, 1998). The key components of differentiation, then, include an individual's level of fusion versus emotional cutoff and I position versus emotional reactivity (Skowron & Friedlander, 1998).
According to Bowen (1978), differentiation of self is essential for healthy psychological development. Poorly differentiated individuals are thought to experience higher levels of chronic anxiety and thus more psychological and physical symptoms. Research has provided some support for this theoretical notion in that lower levels of differentiation have been associated with greater amounts of chronic anxiety and more symptomatic distress (Skowron & Friedlander, 1998), higher frequencies of health problems and greater psychological distress [Bray, Harvey, & Williamson, 1987; Harvey & Bray, 1991; Harvey, Curry, & Bray, 1991), and lower levels of marital satisfaction (Skowron, 2000).
Bowen (1978) theorized that an individual's level of differentiation is largely predicted by the emotional health (i.e., differentiation levels) of his or her parents. Specifically, through a process in which anxiety and unresolved emotional attachments are projected onto children by parents, differentiation levels are passed along through the generations. Research has provided support for this concept of multigenerational transmission process and has identified factors in the family of origin (e.g., conflict, poor communication, divorce, and family dysfunction) that seem to predict differentiation levels of young adult children (Bartle & Anderson, 1991; Harvey et al., 1991; Johnson & McNeil, 1998; Johnson & Nelson, 1998).
I know a lot of people who have grown up in horrible families and who appear to be healthy because they have made a conscious effort to "split" from their families and finally move on with their own lives. Many such people often tell me, "As far as I'm concerned, my old family doesn't exist" or "I don't have a family". Something like that. Unfortunately, they don't seem to realise that in doing so, they have not resolved the issues with their families and all the effort they put into "splitting" from them is utterly draining. Indeed, far from being "split" from their families, they remain intimately intertwined with them, with images of conflict and disappointment constantly popping up during weak moments or during sleep. Clearly, something wants to get out from under the surface, but these people aren't letting that natural process of closure and healing take place.
The greater sign of health would be the person who acknowledges honestly that her family was horrible to her, that she remains upset and disappointed, and that she now wants to move on with her life. Here, there is a full, non-varnished, non-defensive integration of both good and bad emotions. This person realises that these feelings will not kill her (ie, that she can be disappointed with her family and not die as a result); in fact, the more the feelings are integrated into consciousness, the quicker they fulfill the role (which is to motivate us to do something about the situation, even if that is just getting away from the situation and moving on with one's own life) and the quicker they dissipate. Feelings linger only when we don't listen to them and follow their advice. When we acknowledge the feelings (both the good and the bad)—and then let them do their job—they go away. Then we have mental health.