Passage Summary: Scientists know that stress and weak immune systems are linked to cancer. Because support groups help people relax, they might actually help treat the disease.

Conclusion: Support groups for cancer patients may provide legitimate medical benefits.

Reasoning: Weakened immune systems make people more susceptible to cancer, and participating in support groups is known to lower stress.

Analysis: The psychologist is making a significant leap from 'reducing stress' to 'therapeutic value' via the immune system. For this argument to hold water, there must be a functional link between stress levels and the immune system's ability to fight cancer. We are looking for a necessary assumption that bridges this gap—specifically, that reducing stress actually bolsters the immune system or otherwise aids recovery. Without this connection, the fact that groups reduce stress would be medically irrelevant to the cancer itself.