Table 1.

Author	N	Sample	Diagnosis	Current or retrospective reports	How symptoms Measured	How Episode Status Determined	Control over Medication	Control over Potential Confounds	Findings in Comparing Unipolar (UP) with Bipolar (BP) Depression
No controls over confounds or medications
Abrams and Taylor (1980)	40	inpatients with diagnosis of endogenous depression	psychiatric diagnosis using semi-structured interview	current	interviewer rated depressive, manic, and catatonic symptoms	all patients admitted during depressive episode	none	none	UP: greater weight loss and more sxs no difference on number of episodes per year, hx of xubstance or ETOH abuse, ADHD, seizures, or head trauma
Black and Nasrallah (1989)	1715	inpatient BP and primary UP	psychiatric	retrospective	chart review	chart review of admission diagnosis using DSM-III criteria	none	none	no difference in frequency of psychosis
Brockington et al. (1982)	154 (London) 102 (Chicago)	inpatient schizoaffective-depressed, MDD, & minor depressive disorder in UP group; BP=hx of definite or probable mania	chart review	current	Present State Examination (PSE)	all patients admitted during depressive episode	none	none	London UP: depression less severe in AM, less derealization, greater suicidality, more ideas of reference, more auditory hallucinations, greater loss of insight, greater observed anxiety; Chicago UP: less mood lability, fewer somatic complaints, less haughty attitude, more unvarying depression, more initial insomnia, more muddled thoughts
Guze et al. (1975)	253	inpatient UP or BP with either primary or secondary affective disorder	structured interview	retrospective	interviewer	no distinctions between episodes	none	separate comparisons between primary and secondary disorders	UP: fewer hospitalizations, more psychosis
Lester (1993)	meta-analysis of 23 studies	studies comparing suicidal behavior in patients with bipolar and unipolar disorder	varied	varied	varied	no distinction between manic and depressive episodes in most studies	varied	none-age and sex often not reported	no significant difference in completed suicides, although result is due to one large deviant study; BP had significantly more subsequent suicide attempts; studies split on differences in previous suicide attempts; single studies found significantly greater combined previous and subsequent suicide attempts and ideation in UP; studies comparing BP I and II disorders split on difference in previous and subsequent suicide attempts
Statistical control over confounds
Breslau and Meltzer (1998)	111	voluntary-admission inpatients with psychotic depression	PSE, psychiatric and family history schedule, and Hamilton Rating Scale for Depression (HRSD) for diagnosis of schizoaffective, unipolar, or bipolar disorder or per RDC criteria at discharge	current	Schedule for Affective Disorders and Schizophrenia-C (SADS)	all patients admitted during depressive episode	none	no significant differences in sex, ethnicity, age at admission, or age at onset	in UP and BP depressions, no significant differences on any particular symptom among comparisons of individual SADS-C psychotic symptoms; only significant difference was greater hypomania in BP on comparison on nonpsychotic SADS-C symptoms
Coryell et al. (1989)	559	inpatient and outpatient BP I, BP II, and UP	SADS using RDC criteria	prospective over 5 years	Longitudinal Interval Follow-up Evaluation (LIFE)	all patients entered study during depressive episode	medications converted into drug equivalency scores	no significant differences in age or sex	no difference in GAS scores, suicide, symptoms of RDC syndromes, or endogenous subtype
Statistical control over confounds
Parker et al. (2000)	987	inpatient and outpatient BP and UP	chart review	retrospective	DSM-III, Clinical, CORE	DSM-III defined major depressive disorder	none	no significant differences in age or sex	UP: less psychotic depression or melancholia, to have appetite loss, slowed thinking, indecisiveness, psychomotor retardation, loss of interest, anticipatory anhedonia, non-reactivity of mood, pathological guilt, delusions, or hallucinations; more likely to be diagnosed with reactive depression and to have non-variable mood
Matched on potential confounding variables
Endicott et al. (1985)	292	inpatient recurrent unipolar, BP I, and BP II	SADS using RDC criteria	current and retrospective	observation, chart review, family interviews	all patients admitted during depressive episode	none	all data analyzed between groups matched on sex; no significant difference in age	UP: less lifetime psychotic major depression, less frequent moderate suicidal intent; less primary depression, intake episode more likely to include major depressive period; no significant difference in endogenous depression
Mitchell et al. (1992)	54	inpatients and outpatients	diagnosis of BP or UP depression that meets DSM-III, RDC, and CORE criteria for melancholy or endogenous depression; BP meet RDC criteria for past manic or hypomanic episodes	current	semi-structured interview to evaluate present episode & mental state signs; previous medical records	all patients in depressive episode	none	BP and UP matched on age, sex, and endogenous depression; no difference in psychosis or depression severity	in comparisons of 31 mental state signs and 37 symptoms, no significant difference on index of psychomotor change; unipolars significantly more likely to have slowed movements; bipolars significantly more likely to be nihilistic; nonsignificant trends for bipolars to be less retarded and more agitated
Mitchell et al. (2001)	78	inpatient and outpatient BP and UP	DSM-IV criteria for major depressive disorder or bipolar disorder	current	HRSD, Newcastle Endogenous Depression Diagnostic Index, CORE	current diagnosis meets DSM-IV criteria for major depressive disorder	none	matched on age, sex, and melancholic subtype	UP: less likely to have psychomotor-retarded atypical and melancholic symptoms, less likely to have had psychotic depresion; no difference in depression severity
Control over medication and some control over confounds
Beigel and Murphy (1971)	50	inpatient BP and UP in psychotic depressive episodes	psychiatric, interviews with family, and chart review; BP had to have documented manic episode on research ward	retrospective	Bunney-Hamburg 15-point nurse rating scale	all patients admitted during depressive episode; all patients had at least 2 weeks clinical ratable depression and at least 3 days without manic symptoms before and after rating period	14 day drug washout	matched on age, sex, and depression severity	UP: greater pacing, overt anger, and somatic symptoms; no significant differences in anxiety or psychosis (although trend for UP to have greater anxiety)
Borkowska and Rybakowski (2001)	45	inpatient BP and UP	psychiatric using ICD-10 or DSM-IV criteria	current	HRSD	all patients admitted during depressive episode; excluded if psychotic or manic symptoms present	no ECT within 1 year prior to study; mood stabilizers washed out 1 month prior to study; all drugs washed out 7 to 10 days prior	no significant differences in education, severity of depression, or duration of illness	BP showed greater frontal lobe cognitive dysfunction, particularly in strategy shifting, visiospatial working memory, and executive functioning on administration of various neuropsychological tests
Giles et al. (1986)	44	BP I, BP II, and endogenous unipolars	SADS-L using RDC criteria	current	HRSD	interview with HRSD (no cut-off published)	drug washout for 14 days prior to study entry	matched on age, sex, and depression severity	BPII: greater REM latency and total sleep time compared to UP (total non-REM sleep explained greater sleep total), no significant differences in % time in each stage of sleep; no significant differences between BP I and BP II or BP I and UP
Gurpegui et al. (1985)	27	consecutively-admitted inpatients diagnosed with endogenous UP depression or BP depression	psychiatric per ICD-9 criteria	current	Comprehensive Psychopathological Rating Scale, HRSD	all patients admitted during depressive episode	one-week drug washout; exclusion criteria included the use of lithium within 6 months prior to admission	no significant differences in sex, age at admission, or age at first depressive episode	subsequent to dexamethason suppression test and thyrotropin releasing hormone stimulation test, unipolars had significantly more frequent and higher scores for weight loss, reduced appetite, muscular tension, and autonomic disturbances; hostile feelings was the only elevated symptom in the bipolar depressed patients
Katz et al. (1982)	74	inpatient UP and BP I	psychiatric	current	HRSD, SADS-C, interviewer ratings, self-reports, psychomotor performance	all patients admitted during depressive episode	all patients administered tricyclics (either amitryptiline or imipramine)	none	baseline: UP: greater anxiety, agitation, somatization, and depression; after 2–3 weeks of tricyclic treatment: UP: less anxiety, agitation, and psychoticism than BP
Kuhs and Reschke (1992)	37	patients who met criteria of both major depressive episode according to DSM-III and endogenous depression per ICD-9	psychiatric diagnosis of either UP or BP depression	current	HRSD	all patients in depressive episode	22 out of 25 UP patients and 9 out of 12 BP patients receiving antidepressant medication; 10 out of 25 UP and 6 out of 12 BP patients receiving benzodiazepines	no significant difference in depressive inhibition or HRSD score at baseline	no significant difference in actometrically-registered or subjectively-rated psychomotor activity/restlessness and sleep time once unipolars and bipolars matched for age and gender
Kupfer et al. (1974)	11	psychiatric, mental status exams, self reports	current	interviews, staff ratings, self reports, activity measured telemetrically	all patients admitted during depressive episode	baseline measures after 14 day drug washout; 2nd time period 3 weeks after drug treatment (150 mg amitryptyline for UP; lithium level 0.9–1.2 mEq/liter for BP	norelationshipbetween telemetric activity and depression scores		UP: greater psychomotor activity at baseline (differences explained by greater anxeity in UP group); at 2nd measurement no significant difference; as UP improved activity decreased; as BP improved activity increased