I got an interesting inquiry from a reader that I thought I'd post (with their permission) here, along with my (heavily revised with references added) reply. While they ask about a particular self-help guru, my answer applies to lots of approaches, not just this one, so I edited out the specifics.
"I was wondering what do you think of XXXXX? I keep stumbling on [him/her] and [he/she] looks pretty motivating to me. I've read [insert book title], did the exercises and it helped, but I wonder, should I carry on working with that book given the fact that I've recently discovered that XXXXX studied in the field of [something quacky sounding], AND [he/she] suggested [a book, not by him/her, that sounds pretty quackish] for advice!
Sounds pretty shady to me, and I couldn't help but feel incredibly disappointed, since I really look up to XXXXX! Regardless though, [his/her] book helped me, so I was kind of frightened at the fact that the positive effects from the book might be a placebo one, even if the advice sounds pretty realistic! HELP!"
Here's what I have to say about that. My sense is that [the quacky approach] is definitely suspect, at best in the realm of "placebo" - one of those things that gets added onto therapy but doesn't seem to offer any benefit above and beyond. That doesn't mean it's not helping you, though, and here's why you shouldn't feel bad about it:
Reason 1: The placebo effect is real
Ok, so some stuff is supported by research and other stuff, we're not so sure. All sorts of practices that have been "discredited" continue to help people. Acupuncture, for example, has received all sorts of criticism as being quackery. However, other research suggests that placebo treatments are effective for pain management, and even produce objective results in the brain (Wager et al., 2004). In other words, the placebo effect is not just something you imagine - in some cases, it causes real benefits.
Reason 2: Strategies that you believe in work better
There are a lot of strategies out there, and those that seem most plausible to you are most likely to benefit you. In one study, for example, participants were asked to practice gratitude; some believed it would be helpful and others did not, and only the ones who believed it would be helpful benefited, despite doing the exact same activity (Sin, Della Porta, & Lyubomirsky, 2011). So while research provides recommendations about which activities "work" the best (and maybe those recommendations don't include whatever you are doing), these conclusions should be tempered with the reality that if you don't believe in it, it won't help. if you love XXXXX's book, that belief helps the book to help you.
Reason 3: The cause of your improvements might not even be the placebo effect
So your belief about the helpfulness of an activity makes it more effective. One might argue that that's the textbook definition of the placebo effect, but allow me to offer an alternative: maybe people who believe in a strategy find a way to make it helpful. A common "control" condition in happiness activity studies is to keep a log of everything you did each day. It's not intended to help, but it takes enough time that it kind of feels like it could be helpful. Why, then, do some people in these control conditions benefit? Anecdotal evidence suggests that they tweak it and personalize it, using the activity as a way to organize their daily schedule and make the best use of their time. My guess is that that's what you (I am now speaking to the reader who wrote to me) are doing here — taking something that might or might not be helpful, discarding the bad parts, keeping the good parts, and making it work for you. Nothing wrong with that!
Wait, so it doesn't matter whether something is scientifically-based or not?
I wouldn't go that far. But I would say that, in the grand scheme of things, if you love some self-help approach that you fear might be snake oil, don't worry about it too much unless you are using it to the exclusion of other approaches. A recent study suggests, however, that this is unlikely — the average happiness seeker reports that they use 7-8 different happiness strategies on a regular basis (Parks et al., in press, Study 2, spearheaded by Matt Della Porta). And further research suggests that more variety in the activities you practice translates into more improvement in your happiness (Parks et al., in press, Study 3, spearheaded by Russell Pierce). So spread yourself around! Try out different things. Not only will you be fine, you might even be better because of it.
Parks, A.C., Della Porta, M.D., Pierce, R.S., Zilca, R., & Lyubomirsky, S. (in press). Pursuing happiness in everyday life: The characteristics and behaviors of online happiness seekers. Emotion.
Sin, N.L., Della Porta, M.D., & Lyubomirsky, S. (2011). Tailoring positive psychology interventions to treat depressed individuals. In S.I. Donaldson, M. Csikszentmihalyi, & J. Nakamura (Eds.), Applied positive psychology: Improving everyday life, health, schools, work, and society (pp. 79-96). New York: Routledge.
Wager, T.D., Rilling, J.K., Smith, E.E., Sokolik, A., Casey, K.L. et al. (2004). Placebo-induced changes in fMRI in the anticipation and experience of pain. Science, 303, 1162-1167.