It seems wise to avoid electroshock. Yes, placebo helps but you can enjoy a placebo advantage with any medicinal agent or procedure, no need to choose such a risky means of care as electroshock.
A health care power of attorney document can speak for you when you are not able to clearly express your preferences. Along with that document you can designate a friend as your health care agent, the person best able to ensure your care wishes are followed.
Many states provide templates for creating these documents. They can benefit anyone but are especially useful for handicapped people or advanced elders, anyone who wants to avoid electroshock.