Why a study on using positive thinking to treat depression has me cynical, not hopeful

From the BBC:

Cardiff University researchers used MRI scanners to show eight people how their brains reacted to positive imagery.

After four sessions of the therapy the participants had seen significant improvements in their depression.

The most glaring critique of this research is the sample size: only eight people?! The people conducting the research acknowledged that more research is necessary, however. That's not why I'm feeling cynical about the study, however.

On the surface, this looks like something that could potentially help some people manage their depression. There's nothing wrong with that. My concern is how this will feed into the narrative that people with depression might feel better if they just think positively!

Yes, because thinking wonderful thoughts is the secret to flight and the cure for depression.

Obviously, this attitude aggravates me to no end. It's easy for someone who isn't mentally ill to conjure up happy thoughts. Someone with depression, on the other hand, might find that a bit more difficult. It's important for any article discussing mental illness and possible new treatments to be aware of the stigma and prevalent narratives surrounding said illness, and to ensure that the article doesn't further those things.

Yes, this research has potential. I won't be pleased if people who are not familiar with depression cite it when telling a depressed person to think happy things, though.