Apoptosis, or programmed cell death, is a crucial biological process, but the provided text focuses on environmental factors affecting optimism and pessimism, not the causes of apoptosis. Therefore, based solely on the provided text, it is impossible to answer the question regarding the common causes of apoptosis. The reference discusses the influence of family environment on personality traits, not cellular processes.
Due to the mismatch between the provided reference and the question, I cannot provide an answer. I would need references pertaining to apoptosis to accurately address this question.
