Are stipends considered self employment income?

Not if you were an employee of the entity issuing the stipend.

It will depend on the circumstances under which the stipend was issued.

According to the IRS:

A stipend is defined as a fixed sum of money paid periodically for services or to defray expenses. The fact that remuneration is termed a "fee" or "stipend" rather than salary or wages is immaterial. Wages are generally subject to employment taxes and should be reported on Form W-2, Wage and Tax Statement.Refer to Publication 15, Circular E, Employer's Tax Guide,section 5, Wages and Other Compensation, for rules on accountable and nonaccountable plans for employee business expenses.

The income from stipends is reportable. Is the stipend or fee paid to an employee or an independent contractor reportable? The answer to this question determines the way that the stipend is reported. See also the section entitled Employee vs. Independent Contractor.