What is the meaning of the mitzva of visiting the sick. Is it just to pay attention to the ill person, or does it have any curative effect on the person as well?
Visiting the sick is a specific form of doing chesed (acts of loving-kindness) with our fellow human being.
On a simple level it is certainly true that visiting the sick expresses sympathy and empathy with his difficult position, and is a way of letting him know that people actually care.
However, since a person’s physical state is often related to his internal emotional or mental state, a sick visit can often improve a person’s feelings in a way which literally makes the person feel better.
The effect of emotions and thoughts on the body is obvious. Consider a healthy person who is perturbed by disturbing feelings or thoughts. Despite his health, he is likely to be in a state of apathetic paralysis. On the other hand, even a weak and sickly person can be moved to action through passionate feelings and convictions.
This is the meaning of the teaching of the Sages who claimed that one who visits the sick takes 1/60th of, i.e. alleviates, his sickness (Baba Metzia 30b).
One explanation of the way this works is that when one visits the sick, the visit itself, and even more so the conversation and attention bestowed upon the person, uplifts his spirits, and the resulting positive energy actually aids the soul to heal the body.
Another way that visiting the sick actually improves the person’s condition is through the power of prayer.
When we see the ill person suffering, our compassion and hope for his recovery should be channeled toward conferring upon him a blessing of recovery and praying to G‑d on his behalf, in his presence and otherwise, throughout one’s prayers.
The benefit of this is two-fold. First, it inspires within the sick person hope for recovery which is certainly an important ingredient for getting better. Second, the blessings and prayers themselves actually have a power to bring cure and healing to illness.
In both ways, by the fueling of hope and power of prayer, the more people who are involved, the stronger effect it will have on the sick person and the more it will contribute to his recovery.
Therefore, one must not take the approach that since others have visited, he is exempt. But rather to the extent to which it can be assumed the sick person would appreciate the visit, he should go out of his way to fulfill this very important mitzva of chesed!