I don't know anything about him, but based on his wikipedia article, I wouldn't put any stock at all in his journalistic skills. https://en.wikipedia.org/wiki/Johann_Hari
That's OK. Admittedly, if I had read that before, I may have seen his work more skeptically but I would still probably have engaged. With a lot of journalists reporting on science, if I can, I try to dig deeper into the studies they quote and go to the primary sources. Other times I probably just judge what they're saying based on my gut and intuition, trying to take shortcuts and hoping it's right :-)