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Psychiatric problems may be the cause or the effect of many toxicologic ­presentations. Suicide attempts and aggressive behaviors are commonly associated with toxicity and can be uniquely difficult to assess and manage. Patient behaviors are often viewed dichotomously as either totally intentional and deliberate or totally “out of control” and irrational. The truth is usually more complex, with some aspects occurring within the awareness and control of the patient and other aspects either unknown or overwhelming to the patient. Neuropsychological conceptions of “behavioral disinhibition”­ as a baseline personality trait that is relatively fixed are complementary to presumed organic etiologies of disinhibition such as intoxication or brain injury; in the latter cases, frontal lobe dysfunction is directly implicated. Yet more subtle frontal lobe dysfunction is likely occurring in many patients without such a direct neurological insult: patients with psychosis or mania, personality disorders, attention-deficit/hyperactivity disorder, or even agitation in the context of psychological distress. A patient’s innate capacity for self-restraint can vary widely, and some will present with behavioral disturbances much more readily than others.112

Issues of capacity often arise with intoxicated or impaired patients, and the basic approach to capacity assessment will be covered. “Medical ­clearance” is usually requested prior to a patient’s transfer to psychiatric care, yet this has proven to be a rather vague concept that lacks a standard protocol; however, there are practice guidelines addressing this issue, which will be discussed. This chapter also explores the topics of suicide/self-harm and violence to enable the physician to adopt the appropriate role of both diagnostician and medical decision-maker. Finally, substance use disorders (SUDs) will be addressed, given that they are problematic in the emergency setting and highly comorbid with suicidality and violence.


Physicians are legally and ethically required to obtain informed consent before treating a patient to allow the patient to make a voluntary choice about his or her care. However, if a patient is cognitively impaired, the physician must make a careful assessment of capacity and proceed as medically necessary should the patient be found to lack capacity. It does not matter whether the cognitive impairment is due to psychiatric illness, medical illness, or a transient xenobiotic-induced delirium; if the patient is unable to make a logical and rational decision stemming from his or her personal value system, the physician can override the patient’s autonomy to provide necessary care.7 Traditionally, the term “competence” denotes a legal status determined by a court of law, whereas “capacity” is assessed by a physician in a clinical setting. The distinction between these terms has become blurred in both the medical and legal literature, but it is a helpful framework nonetheless.7

It is important to note that capacity assessments occur at a specific moment in time regarding a specific medical decision. The assessment is not a “global” determination that persists throughout the hospitalization or even the ...

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