I've treated many people for panic attacks and generalized anxiety. Some of what is being described here could possibly be considered a panic attack, especially the unexplained episodes in very experienced divers. The weird thing about panic attacks is that they can happen at any time with little to no provocation. Also, they are controlled by the sympathetic nervous system but there are mental feedback things that you can do (biofeedback, yoga, meditation) to help. I see panic attack frequently in men, aged 25-35, often type A personalities. I've often wondered if it has to do with stuffing the stress down inside for so long, until the body becomes overwhelmed by stress hormones.
The problem with panic attacks is that most of the signaling is going on in the amygdala, a fairly primitive part of the brain. This is also the part of the brain that is effected by PTSD. ( post-traumatic stress disorder). This makes it pretty hard to "talk yourself down" from a true panic attack.
Panic attacks are not a sign of mental weakness, although they could certainly kill you under water.
I have PTSD, which is in the panic disorder family, so I can relate to the feelings of panic. I've also had a couple of near-panic episodes underwater, brought on from task and physical overload, usually when my mask was flooded or off. ( I have to work on that, especially in cold water) My PTSD is generally very well controlled nowadays by a men's prostate medicine, also used for blood pressure. It's an alpha blocker called prasazosin.
Here's a good description of panic attack from Wikipedia:
Sufferers of panic attacks often report a fear or sense of dying, "going crazy," or experiencing a
heart attack or "flashing vision," feeling
faint or
nauseated, a numb sensation throughout the body, heavy breathing (and almost always,
hyperventilation), or losing control of themselves. Some people also suffer from
tunnel vision, mostly due to blood flow leaving the head to more critical parts of the body in defense. These feelings may provoke a strong urge to escape or flee the place where the attack began (a consequence of the sympathetic "
fight-or-flight response") in which the hormone which causes this response is released in significant amounts. This response floods the body with
hormones, particularly
epinephrine (adrenaline), that aid it in defending against harm.
[3]
A panic attack is a response of the
sympathetic nervous system (SNS). The most common symptoms may include
trembling,
dyspnea(
shortness of breath),
heart palpitations,
chest pain (or chest tightness),
hot flashes, cold flashes, burning sensations (particularly in the facial or neck area),
sweating,
nausea,
dizziness (or slight
vertigo),
light-headedness,
hyperventilation,
paresthesias (tingling sensations), sensations of
choking or
smothering, difficulty moving and
derealization. These physical symptoms are interpreted with alarm in people prone to panic attacks. This results in increased anxiety, and forms a
positive feedback loop.
[7]
Often, the onset of
shortness of breath and
chest pain are the predominant symptoms; the sufferer incorrectly appraises this as a sign or
symptom of a
heart attack. This can result in the person experiencing a panic attack seeking treatment in an
emergency room. However, since chest pain and shortness of breath are indeed hallmark symptoms of cardiovascular illnesses, including
unstable angina and
myocardial infarction (heart attack), especially in a person whose mental health status and heart health status are not known, attributing these pains to simple anxiety and not (also) a physical condition is a
diagnosis of exclusion (other conditions must be ruled out first) until an electrocardiogram and a mental health assessment have been carried out.
Panic attacks are distinguished from other forms of anxiety by their intensity and their sudden, episodic nature.
[3] They are often experienced in conjunction with anxiety disorders and other
psychological conditions, although panic attacks are not usually indicative of a
mental disorder.