Table 3

The input symptoms, intermediate variables and bias variables for the diagnosis of dysthymic disorder based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision

Classification of symptoms	Criterion variable	Major or minor criteria (domains)	Intermediate variables	Symptoms	Symptom variables	Equations to generate diagnosis or domain variables	Approximation	Mechanisms related to introducing biases
Dysthymia (variable=dys)						dys=dys_ma x dys_mi	dys=intercept + coef1 x dys_ma+coef2 x dys_mi+coef3 x dys_bias	Multiplication to create the situations where both the major and minor criteria met (union of two binomial variables, mde_ma x mde_mi) and the bias variable (dys_bias) equivalent to the residual of the diagnosis not explained by the input symptoms and the bias variables due to censoring and categorisation
Major criteria, essential for diagnosis
		Depressed mood most of the day for more days than not, for at least 2 years	dys_ma
Minor criteria (at least two items)			dys_mi			dys_mi=dys_mi1+dys_mi2+ dys_mi3+dys_mi4+dys_mi5+ dys_mi6+dys_mi_bias		Categorising of the sum of multiple input variables
		Poor appetite or overeating	dys_mi1			dys_mi1=dys_mi1_1+ dys_mi1_2+dys_mi1_bias		Censoring of the sum of multiple input variables
				Poor appetite	dys_mi1_1
				Overeating	dys_mi1_2
				Information of the domain not explained by the input variables	dys_mi1_bias
		Insomnia or sleeping too much*	dys_mi2/mde_mi4			dys_mi2=mde_mi4= mde_mi4_1+ mde_mi4_2+mde_mi4_bias		Censoring of the sum of multiple input variables
				Insomnia	mde_mi4_1
				Sleeping too much	mde_mi4_2
				Information of the domain not explained by the input variables	mde_mi4_bias
		Low energy or fatigue*	dys_mi3/mde_mi6			dys_mi3=mde_mi6= mde_mi6_1+mde_mi6_2+ mde_mi6_bias		Censoring of the sum of multiple input variables
				Fatigue	mde_mi6_1
				Loss of energy (low energy)	mde_mi6_2
				Information of the domain not explained by the input variables	mde_mi6_bias
		Low self-esteem	dys_mi4
		Poor concentration or difficulty making decisions*	dys_mi5/mde_mi8			dys_mi5=mde_mi8= mde_mi8_1+mde_mi8_2+ mde_mi8_bias		Censoring of the sum of multiple input variables
				Diminished ability to think or concentrate (Poor concentration)	mde_mi8_1
				difficulty making decisions (indecisiveness)	mde_mi8_2
				Information of the domain not explained by the input variables	mde_mi8_bias
		Feelings of hopelessness	dys_mi6
		Information of minor criteria not explained by input variables	dys_mi_bias					Bias introduced by categorising the number of input symptoms confirmed in the minor criteria
Information of diagnosis not explained by major or minor criteria	dys_bias							Information of the diagnosis not explained by the input symptoms and the bias variables generated due to data categorisation (dys_mi_bias)

*The input symptoms used for the diagnosis of both major depressive episodes and dysthymic disorder.