The most recent data from 2012, released on Friday, reveals that 402,950 people died in Spain, some 15,039 (3.9 percent) more than in 2011.
There were 3539 suicides (2,724 men and 815 women), up 11.3 percent from the year before, a rate of 7.6 per 100,000 inhabitants. The figures were the highest since 2005.
According to official broadcaster RTVE, suicide was second only to cancer (15 percent of deaths) in the overall 25-34 age group, but the leading cause of death in young men (17.8 percent).
Fatalities as a result of traffic accidents fell by 9.5 percent, to 1,915.
30.3 percent of deaths in Spain were the result of circulatory system failures such as heart attacks. This was closely followed by cancer (27.5 percent) and respiratory system illnesses (11.7 percent).
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Nervous system illnesses like Alzheimer's disease were the fourth leading cause of death.
A 21 percent spike in the death rate in February and March compared with the previous year was attributed to a late-breaking flu epidemic. The same period saw deaths as a result of respiratory failure rise 53.6 percent year-on-year.