Table 2.

Summary of cluster characteristics according to the CMHQ data.

	Cluster 1 (n = 46)	Cluster 2 (n = 34)		Cluster 3 (n = 46)	Cluster 4 (n = 44)
Location and quality	(i) Forehead; Back of the head; Top of the head (ii) Pain quality: Throbbing; Pulsating; Pounding; Tight; A “band-like” sensation	(i) Forehead, Back of the head, Top of the head; Both side of the head (ii) Pain quality: Throbbing; Pulsating; Pounding (iii) Worse in the morning; Worse at night; All day		Whole head; No particular location	Explosive; Not dull; Sharp; Piercing
Aggravating and relieving factors	Aggravating by Dehydration; Hunger; Chocolate; Muscular strain (muscle tightness); Poor posture in sitting, standing or sleeping; Teeth grinding	Aggravating by Change of weather; Change in temperature; Hot weather; Cold weather; Dehydration; Hunger; Chocolate	Relieving by Exercise; Massage; Pressing the pain area; Warmth Coldness; Medication; Eating	Aggravating by Stress; Nervousness Irritability Excessive worry; Depression Tension or conflict-related	Aggravating by Windy days; Damp weather/Humid weather; Rainy days
Accompanying symptoms	Sensitivity to light (or to bright lights); Sensitivity to sound	“Pins and needles” or numbness in the hands and feet; Faintness; Dizziness; Watery bowel motion; Loose bowel motion		Dry mouth; Thirst; Bitter taste in the mouth	Belching; Bloating/Flatulence; Indigestion; Fear of being hot

Cluster 1: ascendant hyperactivity of liver yang. Cluster 2: dual qi and blood deficiency. Cluster 3: liver depression forming fire. Cluster 4: unlabelled group.