Really?? I wonder why that is.
Bipolar (aka manic depression) suicides will almost always occur when the person is about to drop off from a manic state. That's why you will often hear their friends and family saying things like that they were doing so well or that they were finally happy with things just before the event. Apparently, the patient, so to speak, knows their syndrome well enough to recognize that a drop is coming up which leads to a bout of serious depression. That's what they can't handle and, unfortunately, sometimes decide to take drastic measures into their hands. Many avoid the Lithium prescribed to them because that has so many bad side effects that they can't deal with.
In the spring, we get more light. Signs that summer is on the way. Many of us, bipolar and others (no, I am not bipolar but I have suffered bouts of major depression since I was 4 years old), get that nice spring fever lift. That can bring on a manic stage for a bipolar. People who suffer with bipolar disorders are usually very affected by light and seasonal disorders (aka SAD). It would seem that March and April is when we get the biggest lift from the benefits from more light (at least, in the northern hemispheres) which would also lead to more manic stages for bipolars; hence more eventual manic drops which bring on more of those going to extremes to avoid the onset of a major depressive stage.
*Clinical depressives (or sometimes referred to as unipolars because they don't get the manic side) are much less likely to go the suicide route because it is believed that they tend to just get too laid back and out of it to bother doing anything about it. Not that it's never happened but it's the bipolars who tend to be needing watched when it comes to serious suicide watches.