I found some information on the characteristics of suicide at this site:
http://www.sccenter.org/understanding.html
Common Characteristics of Suicide
From Definition of Suicide by Edwin Schneidman
The common stimulus for suicide is unendurable psychological pain. Faced with intolerable emotion and unacceptable anguish, people will sometimes opt for a cessation of consciousness. The core ambivalence in suicide reflects the conflict between survival and unbearable stress. The main clinical rule is: Reduce the suffering, often just a little bit, and the individual will choose to live.
The common stressor in suicide is frustrated psychological needs. Suicides are born, negatively, out of needs. Most suicides represent combinations of various needs. The clinical rule is: Address the frustrated needs and the suicide will not occur.
The common purpose of suicide is to seek a solution. Suicide is not a random act. It is a way out of a problem, dilemma, or crisis. It is the answer -- seemingly the only available answer -- to a real puzzler: How to get out of this? It is important to view each suicidal act as an urgently felt effort to answer a question, to resolve an issue, to solve a problem.
The common emotions in suicide are hopelessness and helplessness. Often people on the edge of committing suicide would be willing to live if things -- life -- were only a little bit better, a just noticeable difference. The common fear is that the inferno is endless and that one has to draw the line on one's suffering somewhere.
The common internal attitude toward suicide is ambivalence. Something can be both "A" and "not A." We can both love and hate the same person. A prototypical suicidal state is one in which the individual feels that she or he has to do it, and simultaneously yearns, and even plans, for rescue and intervention.
The common cognitive state in suicide is "constriction" (tunnel vision). Suicide cannot be understood as a psychosis, a neurosis, or a character disorder. It is a transient psychological constriction of affect and intellect. It is a narrowing of the range of options that leads to either/or thinking.
The common interpersonal act in suicide is communication of intention. The communication of suicidal intention is not always a cry for help. First, it is not always a cry; it can be a shout or a murmur or the nonverbal communication of something unspoken. The communication is not always for help; it can be for autonomy or any number of needs. Nonetheless, in most cases of suicide there is some interpersonal communication related to that intended final act.
The common action in suicide is egression or escape. Suicide is a death in which the decedent removes himself from intolerable pain and simultaneously from others in the world.
Suicide is consistent with lifelong coping patterns. "You can't fire me; I quit." "I'll leave her before she leaves me." Schneidman believes that suicide is not a random act, and sometimes is reasonably predictable.
.© 2011 The Suicide and Crisis Center of North Texas
******************************
The same site talks about signs of suicide:
http://www.sccenter.org/teens_signs.html
In the cases of the information above and below the ************* I highlighted those attributes in personality that MAY have (not necessarily do) apply to Dermot's case.
Signs of Suicide
Warning signs of suicide may include:
•
Feelings of sadness or hopelessness
•Anxiety
•A decline in school performance
•Loss of interest in social and sports activities
•Sleeping too little or too much
•Changes in weight or appetite
•Giving away treasured possessions
•Inability to concentrate or think clearly
•
Discouragement about the future
•An increase in drug or alcohol use
•Talk of "going away" or wanting to end it all
•Suddenly becoming very cheerful and happy after being depressed for a long time
.© 2011 The Suicide and Crisis Center of North Texas
It would be interesting to know Dermot's eating and sleeping habits leading up to that early afternoon of January 30, 1972. Did he give stuff away he loved, or lose interest in the things he loved? Even more so, what exactly Dermot did in those three days that led to his disappearance?