Internal validity occurs when the independent variable causes a change in the dependent variable. External validity occurs when the sample is representative of the population and the results can be generalized.
Probability is the likelihood of an event occurring. Variance describes how the values are dispersed around the mean.

This patient does not have a psychiatric history, and his symptoms have only lasted six weeks. Before diagnosing a psychiatric condition, you need to rule out the possibility that his symptoms are the effects of a substance. A urine drug screen is the first step to rule out a substance-induced psychotic disorder.
A CT scan of the brain might also be necessary but at a later time.

The four components of health policy are process, policy reform, policy environment, and policymakers.
Branches of law are the medium through which the components of health policy are developed.

Clomipramine is a tricyclic antidepressant that blocks voltage-sensitive sodium channels in both the brain and the heart. In overdose, tricyclic antidepressants can lead to coma, seizures, cardiac arrhythmia, and death.
Fluoxetine, venlafaxine, and atomoxetine are less likely to be potential causes of this patient's presentation.

Hyponatremia is the most common electrolyte abnormality associated with psychotropic medications.
Medications that are frequently associated with the drug-induced syndrome of inappropriate antidiuretic hormone secretion (SIADH) are oxcarbazepine, carbamazepine, and serotonergic antidepressants.