Reflect on the environmental factors that have —

(a) a positive impact on the being and (b) a negative effect.

Until recently, catastrophic events were not studied systematically, because of their infrequent and unpredictable occurrence. However, because the survivors of these devastating events often experience the severe psychological aftermath termed 'posttraumatic stress disorder'.

Whether large-scale natural disasters produce lasting psychological effects, however, remains a source of controversy. Some research shows evidence of long-term psychological effects, whereas other studies show that the psychological impact of natural disasters is minimal.

In certain respects, the psychological trauma that results from human-produced disasters can be more dramatic and long term in its scope than natural disasters.

Several factors seem to contribute to this phenomenon. One important factor seems to be control. Human-produced disasters are usually the result of human error; but we expect that adequate precautions will be taken to prevent human error. Thus, when disaster strikes, our expectations are violated, leading to a loss of control. In contrast, we do not expect to have control over hurricanes, earthquakes, or other types of natural disasters and accept them as fate.

A second factor has to do with the consequences associated with each type of disaster. Natural disasters, while large in scope, tend to be clearly marked and limited in time. In contrast, human-produced disasters—such as the contamination of ground water with toxic chemicals—can, potentially exert their effects for many years. For example, exposure to toxic chemicals can increase people's risk of developing cancer or produce genetic damage. Moreover, the psychological trauma combined with the uncertainty regarding when or if these consequences will appear can produce chronic stress-related problems.