Two thirds of people who died by probable suicide were not taking the psychiatric medication which had been prescribed for them at the time, a new study has revealed.
The findings have emerged in the post-mortem reports of 153 people who took their lives in the west of Ireland between January 2006 and 2012.
Failure to take antidepressants and antipsychotic medication prior to death by suicide has also been found in other international studies, particularly in people suffering from schizophrenia.
The findings will add to the debate over the "black box" warning on antidepressant medication.
This is a warning saying they could increase the risks of suicidal thinking and behaviour in young people, which was placed by the medicines' watchdog in the United States in 2004.
But the drop in use was followed by a 22pc increase in suicide attempts among teenagers and a 34pc increase among young adults, according to a previous study of millions of young people.
In this latest Irish study, led by researchers at the Department of Psychiatry in NUI Galway, just one person who suffered from schizophrenia had antipsychotic medication detected in their toxicology report.
"It is possible that some individuals had their treatment stopped by a health professional outside the mental health services rather than discontinuing the medication themselves," said the authors in the report, published in the 'Irish Journal of Psychological Medicine'.
Previous studies have also shown that mental health patients who do not take their medication are at higher risk of suicidal thoughts or taking their own lives.
Commenting on the findings, Mater Hospital psychiatrist Professor Patricia Casey said the most telling aspects of the study were the toxicology results.
"In light of the antipathy to medication for the treatment of mental illness, and in particular to antidepressants, it is reasonable to question whether these cultural attitudes influenced the decision to discontinue treatment among the individuals evaluated in this study," she writes in her column in 'Health and Living' today.
If this could be tested by further research, it would make an important contribution to the so-called "black-box debate", she said.
Prof Casey asked: "Is non-treatment adherence and ultimately suicide an unintended consequence of the warning? This question cries out for an answer as life itself is at stake."
The west of Ireland study found that 57 had previously attended mental health services.
Nearly half of this group had had depressive illness, followed by alcohol dependence or misuse. The remainder had diagnoses including schizophrenia, bipolar disorder and anxiety disorders.
Some 65pc had made a previous suicide attempt and 25pc had self-harmed without intent to end life.
There were four times more men than women among the tragedies. One quarter had been sexually abused as children..