LSAT Explanation PT 20, S4, Q8: The symptoms of mental disorders are

LSAT Question Stem

The argument depends on assuming which one of the following? 

Logical Reasoning Question Type

This is a Necessary Assumption question. 

Correct Answer

The correct answer to this question is A. 

LSAT Question Complete Explanation

First, let's summarize and analyze the argument in the passage. The argument is structured as follows:

1. Premise: The symptoms of mental disorders are behavioral, cognitive, or emotional problems.

2. Premise: Some patients with mental disorders can be effectively treated with psychotherapy.

3. Premise: In some patients, mental disorders result from chemical imbalances affecting the brain.

4. Conclusion: These patients (with chemical imbalances) can be effectively treated only with medication that will reduce or correct the imbalance.

To make this argument more accessible, let's use a simple example. Imagine a garden with different types of plants. Some plants need water to grow (psychotherapy), while others need fertilizer (medication). If a plant has a nutrient deficiency (chemical imbalance), it can only be effectively treated with fertilizer (medication).

Now, let's create an "Evaluate" question for this argument: "Can psychotherapy effectively reduce or correct chemical imbalances in patients with mental disorders?"

The question type for this problem is Necessary Assumption, which asks us to find an assumption that the argument depends on. Let's examine each answer choice.

a) Treatment by psychotherapy can produce no effective reduction in or correction of chemical imbalances that cause mental disorders.

This is the correct answer choice. If psychotherapy could effectively reduce or correct chemical imbalances, then medication would not be the only way to treat these patients. The argument relies on this assumption to reach its conclusion.

b) Treatment with medication always shows faster results for patients with mental disorders than does treatment with psychotherapy.

The argument does not mention the speed of results, only the effectiveness of treatment. This answer choice is not relevant to the argument's conclusion.

c) Most mental disorders are not the result of chemical imbalances affecting the brain.

The argument does not need to assume this. Even if most mental disorders had chemical causes, the argument could still hold that medication is the only effective treatment for those specific disorders.

d) Medication is always more effective in treating patients with mental disorders than is psychotherapy.

This answer choice is not necessary for the argument. The argument only claims that medication is the only effective treatment for chemically-caused mental disorders, not that it is always more effective than psychotherapy for all mental disorders.

e) Treatment with psychotherapy has no effect on mental disorders other than a reduction of the symptoms.

The argument does not define "effective treatment," so we cannot conclude that it only refers to symptom reduction. Additionally, even if psychotherapy had other effects on mental disorders, this would not undermine the specific claim about medication being the only effective treatment for chemically-caused mental disorders.

In conclusion, the correct answer choice is (a), as the argument depends on the assumption that psychotherapy cannot effectively reduce or correct chemical imbalances in patients with mental disorders.