Comparison of verbal fluency performance in Kannada-speaking adults with and without euthymic bipolar disorder type 1

Figures & data

Table 1. Demographic characteristics of study participants.

Demographics		Mean (SD)	BD-I n (%)	Mean (SD)	HC n (%)
Age range (years)	25–35	29.37 (4.33)	08 (29.63)	24.75 (2.27)	04 (14.81)
	36–45	41.8 (2.78)	05 (18.52)	40.87 (3.18)	08 (29.63)
	46–55	50.28 (2.81)	07 (25.93)	50.00 (2.56)	07 (25.93)
	56–65	62.86 (3.48)	07 (25.93)	61.12 (2.47)	08 (29.63)
Gender	Male	–	11 (40.74)	–	11 (40.74)
	Female	–	16 (59.26)	–	16 (59.26)
Years of education	3rd–5th	–	07 (25.93)	–	05 (18.52)
	6th–10th	–	07 (25.93)	–	13 (48.14)
	11th–12th	–	05 (18.52)	–	01 (3.70)
	Diploma	–	03 (11.11)	–	03 (11.11)
	Graduate	–	05 (18.52)	–	05 (18.52)
Family history	Positive	–	06 (22.22)	–	–
	Negative	–	21 (77.78)	–	–
Age of onset (years)	15–30	22.68 (6.77)	21 (77.78)	–	–
	40–65	44 (4.04)	06 (22.22)	–	–
No. of hospitalizations	Nil	–	09 (33.33)	–	–
	1–5	–	14 (51.85)	–	–
	6–10	–	02 (7.41)	–	–
	≥10	–	02 (7.41)	–	–
Total no. of episodes	≤20	–	12 (44.44)	–	–
	>20	–	04 (14.81)	–	–
	Unknown	–	11 (40.74)	–	–
Medication	Lithium	–	19 (70.37)	–	–
	Sodium Valproate	–	08 (29.63)	–	–
Comorbid conditions	Diabetes	–	02 (7.41)	–	–
	Hypertension	–	02 (7.41)	–	01 (3.70%)
	Thyroid diff.	–	05 (18.52)	–	–
	Asthma	–	–	–	01 (3.70%)
	Seizures	–	01 (3.70)	–	–

BD = bipolar disorder; HC = healthy controls.

Table 2. Differences in verbal fluency measures of letter and semantic fluency in BD-I and healthy controls.

	BD-1 (n = 27)				HC (n = 27)			Mean Difference (BD vs. HC)	Cohen’s d (BD vs. HC)	p-value
	Male		Female	Total	Male	Female	Total
TNCW	LF	5.73 (3.47)	3.31 (3.32)	4.30 (3.53)	6.45 (2.94)	7.19 (4.90)	6.89 (4.16)	−2.59 (−4.34 to −0.84)	0.67	0.005**
	SF	12.36 (3.14)	11.44 (3.78)	11.81 (3.50)	14.45 (3.21)	15 (4.98)	14.78 (1.79)	−2.96 (−4.81 to −1.11)	0.76	0.003**
NC	LF	2.36 (1.80)	1.19 (1.28)	1.67 (1.59)	2.55 (1.04)	2.81 (2.20)	2.70 (1.79)	−1.04 (−1.84 to −0.23)	0.61	0.013**
	SF	4.18 (1.47)	3.5 (1.55)	3.78 (1.53)	3.82 (0.87)	4.75 (1.98)	4.37 (1.67)	−0.59 (−1.45 to 0.27)	0.37	0.168
MCS	LF	1.49 (0.87)	0.81 (1.03)	1.09 (1.01)	1.48 (0.64)	1.35 (0.85)	1.40 (0.76)	−0.31 (−0.74 to 0.12)	0.34	0.152
	SF	2.11 (0.72)	2.31 (0.93)	2.23 (0.84)	2.55 (1.48)	1.69 (0.52)	2.04 (1.09)	−0.19 (−0.34 to 0.72)	0.19	0.476
NS	LF	2.55 (2.02)	1.63 (1.71)	2.00 (1.86)	3.27 (2.28)	4.19 (2.46)	3.81 (2.39)	−1.81 (−2.73 to −0.90)	0.85	0.001**
	SF	5.73 (2.87)	5.75 (2.82)	5.74 (2.78)	5.91 (2.07)	8.88 (3.96)	7.67 (3.59)	−1.92 (−3.26 to −0.58)	0.59	0.007**

BD-I = bipolar disorder type I; HC = healthy controls; TNCW = total number of correct words; NC = number of clusters; MCS = mean cluster size; NS = number of switches; LF = letter fluency; SF = semantic fluency; M = male; F = female; Cohen’s d interpretation (effect size): 0.2-small, 0.5-medium, 0.8-large. **p < 0.05.

Table 3. Comparison between high and low education in participants with BD-I and HC.

			Low Education [M(SD)] (BD: n = 14; HC: n = 14)	High Education [M(SD)] (BD: n = 13; HC: n = 13)	p-value
TNCW	LF	BD-I	2.5 (2.92)	6.23 (3.14)	0.003**
		HC	5.77 (3.54)	7.93 (4.55)
	Cohen’s d		1.01	0.43
	SF	BD-I	10 (3.16)	13.77 (2.77)	0.001**
		HC	12.77 (3.79)	16.64 (3.95)
	Cohen’s d		0.80	0.84
NC	LF	BD-I	1 (1.36)	2.38 (1.56)	0.085
		HC	2.46 (2.11)	2.93 (1.49)
	Cohen’s d		0.83	0.36
	SF	BD-I	2.86 (1.17)	4.77 (1.23)	0.020**
		HC	4.31 (1.84)	4.43 (1.55)
	Cohen’s d		0.95	0.24
MCS	LF	BD-I	0.68 (0.93)	1.53 (0.92)	0.048**
		HC	1.21 (0.69)	1.57 (0.79)
	Cohen’s d		0.65	0.05
	SF	BD-I	2.45 (0.99)	1.99 (0.58)	0.729
		HC	1.84 (0.64)	2.22 (1.38)
	Cohen’s d		0.716	0.21
NS	LF	BD-I	1.07 (1.44)	3 (1.78)	0.031**
		HC	3.38 (2.39)	4.21 (2.39)
	Cohen’s d		1.18	0.57
	SF	BD-I	4.78 (2.94)	6.77 (2.88)	0.111
		HC	7.23 (3.17)	8.07 (4.03)
	Cohen’s d		0.80	0.39

BD-I = bipolar disorder type I; HC = healthy controls; TNCW = total number of correct words; NC = number of clusters; MCS = mean cluster size; NS = number of switches; LF = letter fluency; SF = semantic fluency; Cohen’s d interpretation (effect size): 0.2-small, 0.5- medium, 0.8- large. **p < 0.05.

Table 4. Temporal pattern of word productivity in BD-I and HC across tasks.

	0 sec–15 sec	16 sec–30 sec	31 sec–45 sec	46 sec–60 sec
Letter fluency
BD-I	2.15(1.77)	1.15(1.03)	0.59(0.80)	0.52(0.85)
HC	3.11(1.99)	1.56(1.63)	1.63(2.10)	1.04(1.56)
Cohen’s d	0.51	0.29	0.65	0.41
Semantic fluency
BD-I	6.59(2.44)	2.59(1.62)	1.78(1.40)	0.89(1.48)
HC	7.67(2.34)	3.19(1.55)	2.33(1.57)	1.67(1.59)
Cohen’s d	0.44	0.37	0.37	0.51

BD-I = bipolar disorder type I; HC = healthy controls; LF = letter fluency; SF = semantic fluency; Cohen’s d interpretation (effect size): 0.2-small, 0.5-medium, 0.8-large.

Table 5. Error frequency and average values for letter and semantic fluency tasks.

Error type	BD-I		HC
	LF	SF	LF	SF
Intrusion, n (%)	6 (22.22)	7 (25.92)	12 (44.44)	8 (29.62)
Mean error	0.30	0.63	0.78	0.45
Perseveration, n (%)	4 (14.81)	19 (70.37)	10 (37.03)	19 (70.37)
Mean error	0.34	1.78	0.82	1.63
Nonwords, n (%)	1 (3.70)	5 (18.51)	2 (7.40)	3 (11.11)
Mean error	0.08	0.26	0.08	0.12

BD-I = bipolar disorder type I; HC = healthy controls; LF = letter fluency; SF = semantic fluency.