There is only one teeny weeny problem. The most common reason for switching drugs is because the therapy doesn't work; when the drugs don't have the desired effect. So it is completely expected that patients who were forced to switch had a worse outcome. They may simply be treatment resistant.
And Pfizer knows this.
That's the reason they use a weasel-sentence in their press release, hidden deep inside the text, saying "As with all observational studies, the findings should be regarded as hypothesis generating."
"The bottom line on this particular study is that the data tell us such switching may not be without consequences," said Michael Berelowitz, senior vice president of Pfizer's global medical division, in a phone interview.
With all due respect, Mr. Berelowitz, it would appear that you are either ignorant on this point or you are lying. An analogy in the mental health field would be if patients who tried Effexor and then switched to a generic tricyclic antidepressant (say, imipramine) were found to have worse depression outcomes than patients who stayed on Effexor. Duh! Again, maybe people who dropped Effexor are treatment-resistant and/or had more severe depression -- medications don't work as well for them. So it would be a pretty stupid comparison to say that those who switched antidepressants were acting dangerously by switching medications, wouldn't it?