Dementamania is director Kit Ryan's second feature; his first, Botched, is apparently 'bat-crap crazy' (to quote a friend who has seen it), and there are definite elements of crazy in this film, in a good way. This is screenwriter Anis Shlewet's first script, and while there are some pacing problems, and something of a lack of a proper buildup of tension, it's a solid story. Ed is certainly far from a likeable guy, with some seriously OCD issues and a nasty temper, but he is interesting, and actor Sam Robertson leads you down a path that makes you care about him in the long run.
As stated, Ed is having strange hallucinations. About zombie-style-biting the neck of a horrible boss; of having sex with a co-worker in the bathroom stall; stabbing another co-worker. All of these seem to be in some egged on fashion, or resulting in an encounter with a strange man, Nicholas, who only Ed seems to talk to. Played at a sufficiently creepy level by Vincent Regan (sufficient in that he's not too scary, and seems to speak in truthful parables), is Nicholas a ghost, a figment of Ed's imagination, or just really good at hiding? The film encourages as much laughter as scares to its benefit.
The pace does drag a bit in the middle. Ed keeps having his hallucinations, but they don't really escalate, each one is pretty equally violent and strange, so there doesn't seem to be a build up of tension that one would expect, especially as the climax is quite dramatic. And the reason for Ed becoming such an asshole, to the point where his hallucinations do have such a strong hold, is well, perhaps insufficient.
At 83 minutes, it's not long, and I wouldn't say it needs to be shorter. But a gradual escalation might have helped the middle section. But overall, this is a highly enjoyable film, with equal parts dark humour and scary darkness, of the very human variety. It's anchored by a strong lead and very good supporting actors, in both drama and comic relief. It's an interesting look at the mundane-ness of life, and how we might be the ones to make it mundane, about how our imaginations can sometimes get the better of us, and how acting out might not always be the best option. Breaking out of a rut is hard, but don't let it start with a wasp's sting.