Case 1: Sensitivity to initial conditions
I.C. is a 25-year-old teacher who is 6 weeks postpartum. Recently, while at a local shopping mall, she experienced a sudden onset of chest discomfort, palpitations, dizziness, trembling, and a sense of impending doom. The episode peaked in intensity within 3 minutes and lasted 20 minutes after leaving the mall. Although she has not experienced another attack, she has progressively limited her activities since, until now, she has not been able to bring herself to re-enter the mall for fear of another attack. In fact, she reports intense anxiety in anticipation of possibly visiting the mall and has begun limiting her driving in general.
Agoraphobia is linked to the location and interpretation of the first panic attack.12 This demonstrates the concept of sensitivity to initial conditions whereby small differences in starting values result in very different behaviors later. In other words, apparently minor differences in a patient’s initial physical and emotional state can translate into drastically different outcomes over time.
This emphasizes the need for physicians to pay attention to detail during stressful events that patients experience. For example, if a patient experiences the first panic attack in a self-perceived “safe” environment or interprets the attack as a normal response, she may avoid the disabling consequence of agoraphobia and remain functional. There are other examples of this sensitivity to small changes, such as siblings of similar genetic make-up and environment who exhibit markedly different health as adults may do so because of “minor” life events each experienced.
Similarly, patients with chronic stable disease who, after a minor event, suddenly change their disease trajectory may be demonstrating sensitivity to initial conditions. This sensitivity has been proposed as an explanation for sudden infant death syndrome13 (SIDS) and “brittle” diabetes.14 Treatment response may depend on sensitivity to initial conditions; cases documenting placebo effects or unpredictable potassium excretion on re-administration of potassium-sparing diuretics are examples.15
Implications for management. Sensitivity to initial conditions has several implications for patient management.
First, we need to recognize the impact it has on patients. Minor life changes can alter the trajectories of patients, so we need to seek the patient’s perspective on stressors they experience. This inherent instability means that “watchful waiting” is a viable approach in some patients because illness may resolve without intervention. It also means that we need to be watchful for signs of an unhealthy trajectory developing in patients even after minor stressors.
Second, sensitivity to initial conditions implies that nonlinear behaviors can change with minor but well-timed interventions. The importance of chronotherapy (timed dosing based on biological rhythms) is receiving increasing attention. Drug efficacy often varies with the time of day.16,17 Though focused on matching circadian rhythms, chronotherapy may be valuable in nonlinear systems if, through our in-depth knowledge of the patient and context, we can identify a point of leverage when an otherwise “ineffective” treatment may be effective for the patient at a specific point in time. There may be justification for re-administering a previously ineffective treatment if you believe the responsiveness of the patient may have changed. Sensitivity to initial conditions may also explain the effectiveness of placebos.
- For the patient above, minimizing the impact of sensitivity to initial conditions requires immediate access to the patient during a subsequent sensitive time. If the patient has a family history of panic disorder or has had panic attacks in the past, you could anticipate that the patient may experience a panic attack in the future and prepare her for it by discussing the chemical basis for panic (and its lack of serious physical consequences) and by encouraging her to contact you day-or-night immediately after experiencing one so that you can help her to identify a nonthreatening (even if illogical) cause for it, thus preventing the fears that lead to agoraphobia.
- For the practitioner, sensitivity to initial conditions emphasizes the need to understand the details surrounding a stressor by asking patients about their perceptions of the events, the circumstances, and how they are being affected by the stressor. Using this sensitivity for treatment implies focusing on the timing of interventions, and considering re-administration of treatments or even the use of placebos.
Case 2: Effects of attractors
A.T. is a 47-year-old factory worker with a 30-year history of alcohol consumption. His daily intake consisted of a case of beer until he quit 3 years ago. He has periodically suffered relapses consisting of 3 or 4 days of binge drinking followed by prolonged abstinence. Although his wife and 2 children are supportive of his efforts at abstinence, his son dramatically increased his alcohol consumption when his father stopped his daily consumption. In addition, his teenage daughter began experimenting with drugs 2 years ago.