Critical Thinking and Depression

Introduction

1. Is there a causal relationship between critical thinking and depression?¹

Critical Thinking

2. Critical thinking is the active, careful and persistent consideration of both the justifications for and the implications of our beliefs (Dewey, 1933, p. 9). Individuals who think critically are more likely to actively, carefully and persistently consider both the justifications for and the implications of their beliefs as compared to individuals who do not think critically.

Depression

3. Depression is a “sad, empty, or irritable mood”, accompanied by related changes that significantly affect the individual’s capacity to function” (American Psychiatric Association, 2022, p. 177).

4. Dysfunctional beliefs (e.g., “If not everyone loves me, then my life is worthless”) are counterproductive, extreme and rigid beliefs thought to develop during childhood and adolescence as a function of negative experiences with parents and significant others, and which serve as the underlying vulnerability to developing depression (Butcher, Hooley & Mineka, 2014, p. 230).

5. The Cognitive Theory of Depression states that there is a causal relationship between the activation of dysfunctional beliefs and depression (Beck, 2009, p. 260). Individuals with activated dysfunctional beliefs are more likely to have depression as compared to individuals without activated dysfunctional beliefs.²

6. There is a causal relationship between the presence of dysfunctional beliefs and the activation of dysfunctional beliefs. This is because an individual has no dysfunctional beliefs to be activated if the individual has no dysfunctional beliefs in the first place. As such, individuals who do not have dysfunctional beliefs are less likely to have activated dysfunctional beliefs as compared to individuals who do have dysfunctional beliefs.³

7. Therefore, there is a causal relationship between the presence of dysfunctional beliefs and depression. This is evident from [5] and [6]. Individuals with dysfunctional beliefs more likely to be depressed as compared to individuals without dysfunctional beliefs.⁴

Critical Thinking and Depression

8. There is a causal relationship between critical thinking and the presence of dysfunctional beliefs. Individuals who think critically are more likely to actively, carefully and persistently consider both the justifications for and the implications of their beliefs as compared to individuals who do not think critically.⁵ If so, then these individuals are also less likely to have dysfunctional beliefs.⁶

9. Therefore, there is a causal relationship between critical thinking and depression. This is evident from [7] and [8]. Individuals who think critically are less likely to have depression as compared to individuals who do not think critically.⁷

Conclusion

10. In conclusion, there is a causal relationship between critical thinking and depression.

References

American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders (5th ed., text rev.).

Beck, A. T., & Alford, B. A. (2009). Depression: Causes and treatment. University of Pennsylvania Press.

Butcher, J. N., Hooley, J. M., Mineka, S. (2014). Abnormal psychology. Pearson Education, Inc.

Dewey, J. (1933). How we think: A restatement of the relation of reflective thinking to the education process. (2nd ed.). D.C. Heath and Company.

Pearl, J. (2018). The book of why. Hachette Book Group.

Copyright © 2024 Lam Fu Yuan, Kevin. All rights reserved.

Footnotes

1. In The Book of Why, Pearl (2018) defines causation in terms of the do-operator: X causes Y if \(P(Y|do(X))>P(Y)\).

2. Let \(D\) denote the event that an individual has depression and \(A\) denote the event that an individual has activated dysfunctional beliefs. Then \[P(D|A)-P(D|¬A)>0\]

3. Let \(B\) denote the event that an individual has dysfunctional beliefs. Then \[P(A|B)-P(A|¬B)>0\]

4. Let \(P(D|A∩B)=a_1\), \(P(D|A∩¬B)=a_2\), \(P(D|¬A∩B)=b_1\), \(P(D|¬A∩¬B)=b_2\), \(P(A|B)=c_1\) and \(P(A|¬B)=c_2\). Then \[ \begin{eqnarray} P(D|B)-P(D|¬B) &=&P(D∩A|B)+P(D∩¬A|B)-[P(D∩A|¬B)+P(D∩¬A|¬B)]\\ &=&P(D|A∩B)P(A|B)+P(D|¬A∩B)P(¬A|B)-[P(D|A∩¬B)P(A|¬B)+P(D|¬A∩¬B)P(¬A|¬B)]\\ &=&P(D|A∩B)P(A|B)+P(D|¬A∩B)[1-P(A|B)]-{P(D|A∩¬B)P(A|¬B)+P(D|¬A∩¬B)[1-P(A|¬B)]}\\ &=&a_1 c_1+b_1 (1-c_1 )-[a_2 c_2+b_2 (1-c_2 )]\\ &=&a_1 c_1-b_1 c_1+b_1-[a_2 c_2-b_2 c_2+b_2 ]\\ &=&(a_1-b_1 ) c_1+b_1-[(a_2-b_2 ) c_2+b_2 ]\\ &=&(a_1-b_1 ) c_1-(a_2-b_2 ) c_2+(b_1-b_2 ) \end{eqnarray}\] Because \(P(A|¬B)=c_2=0\), \[P(D|B)-P(D|¬B)=(a_1-b_1 ) c_1+(b_1-b_2 )\] Assume that \(P(D|A∩B)-P(D|¬A∩B)=a_1-b_1>0\) and \(P(D|¬A∩B)-P(D|¬A∩¬B)=b_1-b_2≥0\). Then \[P(D|B)-P(D|¬B)>0\]

5. Let \(C\) denote the event that an individual thinks critically and \(E\) denote the event that an individual actively, carefully and persistently considers both the justifications for and the implications of his or her beliefs. Then \[P(E|C)-P(E|¬C)>0\]

6. Let \(P(B|E∩C)=p_1\), \(P(B|E∩¬C)=p_2\), \(P(B|¬E∩C)=q_1\), \(P(B|¬E∩¬C)=q_2\), \(P(E|C)=r_1\) and \(P(E|¬C)=r_2\). Then \[ \begin{eqnarray} P(B|C)-P(B|¬C) &=&P(B∩E|C)+P(B∩¬E|C)-[P(B∩E|¬C)+P(B∩¬E|¬B)]\\ &=&P(B|E∩C)P(E|C)+P(B|¬E∩C)P(¬E|C)-[P(B|E∩¬C)P(E|¬C)+P(B|¬E∩¬C)P(¬E|¬C)]\\ &=&P(B|E∩C)P(E|C)+P(B|¬E∩C)[1-P(E|C)]-{P(B|E∩¬C)P(E|¬C)+P(B|¬E∩¬C)[1-P(E|¬C)]}\\ &=&p_1 r_1+q_1 (1-r_1 )-[p_2 r_2+q_2 (1-r_2 )]\\ &=&p_1 r_1-q_1 r_1+q_1-[p_2 r_2-q_2 r_2+q_2 ]\\ &=&(p_1-q_1 ) r_1+q_1-[(p_2-q_2 ) r_2+q_2 ]\\ &=&(p_1-q_1 ) r_1-(p_2-q_2 ) r_2+(q_1-q_2 ) \end{eqnarray} \] Assume that \([P(B|E∩C)-P(B|¬E∩C)]=(p_1-q_1 )≤[P(B|E∩¬C)-P(B|¬E∩¬C)]=(p_2-q_2 )<0\) and \([P(B|¬E∩C)-P(B|¬E∩¬C)]=(q_1-q_2 )≤0\). Then \[P(B|C)-P(B|¬C)<0\] Since \((p_1-q_1 )(r_1-r_2 )<0\) and \([(p_1-q_1 )-(p_2-q_2 )]r_2≤0\), \[ \begin{eqnarray} (p_1-q_1) r_1-(p_2-q_2)r_2 &=&(p_1-q_1)r_1-(p_1-q_1 )r_2+(p_1-q_1)r_2-(p_2-q_2)r_2\\ &=&[(p_1-q_1)(r_1-r_2)]+{[(p_1-q_1)-(p_2-q_2)] r_2 }<0 \end{eqnarray} \]

7. Let \(P(D|B∩C)=x_1\), \(P(D|B∩¬C)=x_2\), \(P(D|¬B∩C)=y_1\), \(P(D|¬B∩¬C)=y_2\), \(P(B|C)=z_1\) and \(P(B|¬C)=z_2\). Then \[ \begin{eqnarray} P(D|C)-P(D|¬C) &=&P(D∩B|C)+P(D∩¬B|C)-[P(D∩B|¬C)+P(D∩¬B|¬C)]\\ &=&P(D|B∩C)P(B|C)+P(D|¬B∩C)P(¬B|C)-[P(D|B∩¬C)P(B|¬C)+P(D|¬B∩¬C)P(¬B|¬C)]\\ &=&P(D|B∩C)P(B|C)+P(D|¬B∩C)[1-P(B|C)]-{P(D|B∩¬C)P(B|¬C)+P(D|¬B∩¬C)[1-P(B|¬C)]}\\ &=&x_1 z_1+y_1 (1-z_1 )-[x_2 z_2+y_2 (1-z_2 )]\\ &=&x_1 z_1-y_1 z_1+y_1-[x_2 z_2-y_2 z_2+y_2 ]\\ &=&(x_1-y_1 ) z_1+y_1-[(x_2-y_2 ) z_2+y_2 ]\\ &=&(x_1-y_1 ) z_1-(x_2-y_2 ) z_2+(y_1-y_2 ) \end{eqnarray} \] Assume that \([P(D|B∩¬C)-P(D|¬B∩¬C)]=(x_2-y_2 )≥[P(D|B∩C)-P(D|¬B∩C)]=(x_1-y_1 )>0\) and \([P(D|¬B∩C)-P(D|¬B∩¬C)]=(y_1-y_2 )≤0\). Then \[P(D|C)-P(D|¬C)<0\] Since \((x_1-y_1)(z_1-z_2)<0\) and \([(x_1-y_1)-(x_2-y_2)]z_1≤0\), \[ \begin{eqnarray} (x_1-y_1 ) z_1-(x_2-y_2 ) z_2 &=&(x_1-y_1 ) z_1-(x_1-y_1 ) z_2+(x_1-y_1 ) z_2-(x_2-y_2 ) z_2\\ &=&[(x_1-y_1 )(z_1-z_2 )]+{[(x_1-y_1 )-(x_2-y_2 )] z_2 }<0 \end{eqnarray} \]