HUMANITY'S uneasy relationship with its home planet may have suffered another blow with suggestions Earth's magnetic field may be linked to suicide and depression.

Oleg Schumilov has found that seasonal peaks in the Earth's magnetic field over a 50-year period coincided with peaks in the number of suicides in the northern Russian city of Kirovsk.

While the Russian researcher told New Scientist his findings did not conclusively prove a causal link, he pointed to other studies suggesting a link between human health and magnetism.

The studies referred to by Mr Schumilov included an Australian analysis of 51,845 males and 16,327 females that found suicides among females increased significantly in autumn during concurrent periods of geomagnetic storm activity.

US Columbia University psychiatrist Kelly Posner told the British weekly magazine that the most plausible suggestion for the association between geomagnetic activity and depression was that magnetic storms could disrupt natural body clocks by desynchronising circadian rhythms and the production of melatonin, a substance in the brain that promotes sleep.