I promise you, Stephen, you are not immune to the placebo effect. None of us are. It is a fundamental artefact of how our brains make cause-effect conslusions. However, I also think implicit in your question is the notion that the “placebo effect” is a real phenomenon, not just an artefact, and that it has real and possibly significant effects on health. I don’t think this is true.
Part of the confusion is in what the term really means. It is usually a catchall used to lump together many psychological and methodological factors that affect the outcome of clinical trials. People tend to think it simply means that believing something is helpful actually makes you better, mind-over-matter and that sort of thing. But it really encompasses much more than that. People getting a medical intervention may appear to get better for many reasons, and without the proper controls (which are rare in medical studies and completely absent in real life), it is impossible to distiguish which are the real causes of perceived improvement in a given case and how much role, if any, psychological factors such as belief or expectancy play. A few examples (from Quackwatch, Why Bogus Therapies Often Seem to Work):
1. The disease may have run its natural course. Many diseases are self-limiting. If the condition is not chronic or fatal, the body’s own recuperative processes usually restore the sufferer to health. Thus, to demonstrate that a therapy is effective, its proponents must show that the number of patients listed as improved exceeds the number expected to recover without any treatment at all (or that they recover reliably faster than if left untreated). Without detailed records of successes and failures for a large enough number of patients with the same complaint, someone cannot legitimately claim to have exceeded the published norms for unaided recovery.
2. Many diseases are cyclical. Such conditions as arthritis, multiple sclerosis, allergies, and gastrointestinal problems normally have “ups and downs.” Naturally, sufferers tend to seek therapy during the downturn of any given cycle. In this way, a bogus treatment will have repeated opportunities to coincide with upturns that would have happened anyway.
3. The placebo effect may be responsible. Through suggestion, belief, expectancy, cognitive reinterpretation, and diversion of attention, patients given biologically useless treatments often experience measurable relief. Some placebo responses produce actual changes in the physical condition; others are subjective changes that make patients feel better even though there has been no objective change in the underlying pathology.
4. People who hedge their bets credit the wrong thing. If improvement occurs after someone has had both “alternative” and science-based treatment, the fringe practice often gets a disproportionate share of the credit.
5. The original diagnosis or prognosis may have been incorrect. Scientifically trained physicians are not infallible. A mistaken diagnosis, followed by a trip to a shrine or an “alternative” healer, can lead to a glowing testimonial for curing a condition that would have resolved by itself. In other cases, the diagnosis may be correct but the time frame, which is inherently difficult to predict, might prove inaccurate.
6. Temporary mood improvement can be confused with cure. Alternative healers often have forceful, charismatic personalities. To the extent that patients are swept up by the messianic aspects of “alternative medicine,” psychological uplift may ensue.
7. Psychological needs can distort what people perceive and do. Even when no objective improvement occurs, people with a strong psychological investment in “alternative medicine” can convince themselves they have been helped. According to cognitive dissonance theory, when experiences contradict existing attitudes, feelings, or knowledge, mental distress is produced. People tend to alleviate this discord by reinterpreting (distorting) the offending information. If no relief occurs after committing time, money, and “face” to an alternate course of treatment (and perhaps to the worldview of which it is a part), internal disharmony can result. Rather than admit to themselves or to others that their efforts have been a waste, many people find some redeeming value in the treatment. Core beliefs tend to be vigorously defended by warping perception and memory. Fringe practitioners and their clients are prone to misinterpret cues and remember things as they wish they had happened. They may be selective in what they recall, overestimating their apparent successes while ignoring, downplaying, or explaining away their failures. The scientific method evolved in large part to reduce the impact of this human penchant for jumping to congenial conclusions. In addition, people normally feel obligated to reciprocate when someone does them a good turn. Since most “alternative” therapists sincerely believe they are helping, it is only natural that patients would want to please them in return. Without patients necessarily realizing it, such obligations are sufficient to inflate their perception of how much benefit they have received.
The job of distinguishing real from spurious causal relationships requires well designed studies and logical abstractions from large bodies of data. Many sources of error can mislead people who rely on intuition or informal reasoning to analyze complex events. Before agreeing to any kind of treatment, you should feel confident that it makes sense and has been scientifically validated through studies that control for placebo responses, compliance effects, and judgmental errors. You should be very wary if the “evidence” consists merely of testimonials, self-published pamphlets or books, or items from the popular media.
There is also a New England Journal of Medicine review which suggests that the common belief placebos have real, significant effects even on symptoms, much less underlying diseases processes, is unfounded.
Ultimately, if someone does something harmless and then feels better, I don’t strongly object to that. But I think the devil is in the details, and the details include unknown risks from therapies presumed to be harmless, avoidance of truly effective therapies as a consequence of the same beliefs that may have a placebo benefit, the ethical concerns about doctors an others selling inert therapies as if they were real therapies, and many others. Rather than an untapped resource for better health, I think the placebo effect is simply an artefact of our epistemological systems which interferes with making accurate judgements about medical interventions, and what benefits it may have are rarely enough to balance the harm done by the effects of such an artefact.
For more info, see:
The Placebo Effect
The Placebo Myth
Studying Placebo Effects
Skeptic’s Dictionary Placebo Entry