Life Events and Stress

Life events research has evolved from early models viewing life changes as inherently stressful and having similar effects on all who experience them to more complex models emphasizing individual differences in both reactions and vulnerability to life events. In addition, there have been a number of conceptual and methodological critiques that have led to more sophisticated models and methods of assessing life events. Recent studies demonstrate that, even with careful attention to methodological issues, life events can have important effects on health and psychological well-being.

Historical issues. Early studies conceptualized life events in terms of the amount of readjustment or change that the events were likely to entail (see Dohrenwend and Dohrenwend; Holmes and Rahe). These studies were based on the assumption that any change in life would be stressful. Particularly influential was the work of Holmes and Rahe, who developed the Social Readjustment Rating Scale (SRRS). The SRRS asked subjects to report the occurrence of life events that had occurred over the previous year, and these events were given life-change unit scores (e.g., 100 for death of a spouse, 28 for an outstanding personal achievement). Total scores were viewed as a measure of life change and as an index of stress. While research with the SRRS did suggest that life events were associated with mental and physical health, limitations to this approach were noted in subsequent work, and conceptual and methodological improvements have been made.

Individual differences in response to life events. Contrary to the assumption that life events have uniform effects that can be measured by life-change units, later studies have shown that the consequences of life events depend on the nature of the events (e.g., whether they are undesirable, unpredictable, or uncontrollable). Growing attention has been paid to subjective meaning of the events to the particular individuals who experience them, rather than the objective occurrence of the events. Since the occurrence of the same event can yield different meanings in each individual, subjective appraisal has been identified as a critical part of the effect life events have on well-being (see Lazarus and Folkman). For example, people generally think that divorce is a stressful experience; however, for some individuals, such as those who have gone through a long-term problematic marriage, divorce can be a resolution of stress and even a relief.

The consequences of life events on physical and psychological well-being are influenced by individual differences in coping resources. When life events occur, individuals' coping resources can buffer the negative consequences of life events and facilitate adjustment. Coping resources may include physical resources (e.g., health and function), psychological resources (e.g., personality traits, values, goals, religious beliefs, self-concept, and self-control), and social resources (social network and social support). One of the most frequently researched psychological resources is mastery, which refers to the extent to when a person feels that he or she has control over his or her life and environment. Individuals with high mastery tend to have a positive perspective on the social environment and believe that they can control or alter their environment. Therefore, those with high mastery are more likely to protect themselves from negative consequences when they face stressful life events.

The impact of social networks and social support has also been widely studied, and there exists a general consensus on their beneficial roles in dealing with stressful life events. It has been found that individuals with persistent deficits in social support experience more stressful life events, higher levels of perceived stress, and greater risk of recurrent depression (see Redinbaugh, MacCallum, and Kiecolt-Glaser). An examination of individuals' personal and social resources is important in understanding individual valances in responding and adapting to stressful life events, and also serves as an important basis for developing effective intervention programs.

Types of life events. Criticisms have been raised concerning the tactic of aggregating total life events to generate an overall score. Many studies on life events have turned the total number of events into a single score by aggregating all life events experienced within a given time frame. This approach treats all events the same, without taking into account the subjectively perceived importance of each event. Since life event inventories cover a variety of events of different importance, equating those events may be insensitive in capturing the significance of different life events, and it may fail to detect the effects of specific events that generate a great deal of stress. Some researchers have suggested the use of a more dimension-specific approach, focusing on specific kinds of events by dividing scales into categories, such as health-related events and loss events.

Retrospective bias in reporting life events. Conventional life event inventories usually ask respondents to read a list of events and report those that occurred to them over a specific time period. The time frames vary from six to eighteen months. Some researchers have raised questions on the accuracy of individuals' memories for life events. In general, people tend to report fewer events for a more distant time period. In addition, a retrospective approach is vulnerable to biasing effects such as selective memory, denial, and over-reporting. For example, depressed people are likely to report more negative events because they tend to focus on the adverse sides of life and to search for events to justify their current moods.

Given this dissatisfaction with the checklist method, researchers have attempted innovative ways to assess life events. Some studies have used combined methods of self-reporting on checklists and interviews. Karen Raphael and colleagues (1991) assessed the occurrence of life events every month for ten months using a checklist, and at the end of the study they did detailed interviews on experience with life events for the studied period. They found that more events were reported on a concurrent monthly basis than were reported on a retrospective interview for the same period. As an alternative to retrospective report over long periods, some researchers have conducted multiple follow-ups for the occurrence of life events, with a very short interval between interviews, in order to detect the onset of events. This approach solves some problems associated with the retrospective report using a checklist method; however, it requires a large sample and longitudinal follow-up.

Life events are not uniform across populations. Some researchers have called into question whether scale items contain relevant and representative life events for target populations. Since scales are rarely generated on the basis of large and well-developed sampling frames, it is hard to judge if the items cover a sufficiently wide range of possible events. More importantly, exposure to life events varies in terms of age, gender, and social roles. For example, retired individuals cannot be promoted, men cannot be pregnant, and unmarried individuals cannot experience marital conflict or divorce. Inclusion of irrelevant items for the target population may result in misclassifying individuals as having fewer numbers of life events.

In response to this concern, a number of life event inventories have been developed for various populations, including the Psychiatric Epidemiological Research Interview (PERI) for general populations; the Life Experiences Survey (LES) for adult age groups; the College Student Life Events Schedule (CSLES) for college students, and the Louisville Older Persons Events Scale (LOPES) for the elderly population.

Confounding of life events and outcomes. Confounding is a particularly important issue in the examination of life events. Many items in life event inventories are closely related to health (e.g., illness, injury, hospitalization), so they can be easily confounded with physical and mental health outcomes. Due to concerns about the confounding of health and life events, some researchers recommend separating health-related life events from non-health-related items. Some studies have selected only healthy elderly individuals in examining the impacts of life events in order to exclude confounding of health variables (see Willis, Thomas, Garry, and Goodwin).

Recent findings on life events and well-being. Numerous studies have examined the consequences of life events on a variety of physical and psychological outcomes. In general populations, life events have been shown to be associated with a variety of physical problems and indicators of psychological distress. However, the magnitude of these associations is often found to be only modest. Researchers have suggested several ways to explain the low associations found in such studies, including methodological issues and individual differences in coping resources.

One fruitful strategy in the study of the effects of life events is longitudinal study of individuals with psychological or physical disorders that tend to have periods of remission and recurrence. For example, it is extremely difficult to demonstrate conclusively that life events provoke the initial onset of depressive disorders, but longitudinal research on individuals with a history of depression provides convincing evidence that life events can lead to recurrence of depressive episodes. Sophisticated longitudinal studies even support the contention that major life events play important roles in onset and recovery from episodes of bipolar disorder and multiple sclerosis—disorders that are commonly viewed as entirely biomedical. Research on life events in these clinical populations has also led to increasing recognition that some life events are caused by the disorders studied; for example, loss of a job may be precipitated by early symptoms of a mental disorder.

Finally, life events have been demonstrated to be potent factors affecting physiological processes, in particular the immune and endocrine systems, with implications for health and recovery from illness. For example, studies of individuals undergoing stressful life events ranging from taking final examinations to experiencing bereavement demonstrate a slowing of wound healing—a finding with clear implications for practical problems such as recovery from surgery.