Does the pineal gland have a role in the psychological mechanisms involved in the progression of cancer?

Psychological factors, e.g., depression and psychological stress have been implicated in the progress of cancer. Similarly, the pineal gland and its principal secretion, melatonin, are known to influence the initiation and progress of cancer. Furthermore, changes in melatonin secretion have been linked with psychological stress and depression, and both the pineal gland and the cerebral cortex act via the limbic system in producing their effects. Both psychological stress and melatonin affect the immune system, as does the hypothalamus and the autonomic nervous system. The pineal gland has both a direct effect on cancer, and via the immune system. Psychological treatment and melatonin treatment have both been found to alleviate the course of cancer clinically. It is thus hypothesized that the pineal gland, and melatonin, are involved in the mechanism of psychological effects in the promotion of the progress of cancer.