Prozac is the most famous of the SSRIs (Selective Serotonin Reuptake Inhibitors), a group of drugs designed to make people feel things are going really pretty well when, in fact, their mind is consistently of the opposite opinion.

It appears to have fallen slightly out of favour, partially because some people are beginning to realise that just because you think everything is going well, there is no guarantee that it actually is.

Among its side effects is a decreased sex drive, which begs the question: just whose definition of happiness is being used?