In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Patients who experienced a manic or hypomanic switch were compared with those who did not on several variables including age , sex , diagnosis ( DSM - IV bipolar I vs . bipolar II ) , number of previous manic episodes , type of antidepressant therapy used ( electroconvulsive therapy vs . antidepressant drugs and , more particularly , selective serotonin reuptake inhibitors [ SSRIs ] ) , use and type of mood stabilizers ( lithium vs . anticonvulsants ) , and temperament of the patient , assessed during a normothymic period using the hyperthymia component of the Semi - structured Affective Temperament Interview .
### Output Text:
Patients who experienced a manic or hypomanic switch were compared with those who did not on several variables including age , sex , diagnosis ( DSM - IV bipolar I vs . bipolar II ) , number of previous manic episodes , type of <span class="chemical">antidepressant</span> therapy used ( electroconvulsive therapy vs . <span class="chemical">antidepressant</span> drugs and , more particularly , selective <span class="chemical">serotonin reuptake inhibitors</span> [ <span class="chemical">SSRIs</span> ] ) , use and type of mood stabilizers ( <span class="chemical">lithium</span> vs . anticonvulsants ) , and temperament of the patient , assessed during a normothymic period using the hyperthymia component of the Semi - structured Affective Temperament Interview . 