I don't know if Will of D is a bot or not, but he's wrong. Take a look at this map of suicide rates on the world (the redder, the higher the rate).
You can see that many countries are anomalous if the lack of sunlight -->suicide theory was remotely true. You have Guyana and Suriname with much higher rates than Brazil and Venezuela, despite sharing the same kind of weather. France and Belgium also have higher rates than Germany and the UK, which have less sunlight. Finally, India and Sri Lanka also have higher rates than countries in the Indochina region despite having similar weather.
And, by now, you should have realized that the pair of countries I listed share much more in common culturally than with the other countries mentioned. So suicide rate has much more with culture than with climate conditions, which is backed up by the ex-Soviet nations having similar suicide rates, Scandinavian countries too, East Europe, Iberic countries, Islamic countries, Latin America countries (with the exception of Suriname and Guyana, who share more in common with each other than with the rest, and Argentina and Chile who suffer the same situation), Equatorial Africa, Hindu countries, China & Japan, US & Canada and Australia & New Zealand.