David Stewart, PH.D.
David Stewart, PH.D. is a Cognitive & Behavioral Psychologist in Cambridge, MA, registered under NPI 1366781932. This provider registers 4 separate taxonomy codes, which usually means they practise across more than one recognised specialty. NPPES records them as a sole proprietor, meaning the practice is not incorporated as a separate legal entity.
Getting there
The practice address on file is 1493 CAMBRIDGE ST, Cambridge, MA 02139. We have not yet mapped what surrounds this office — parking, transit, and nearby pharmacies are added as our data collection reaches each location.
Credentials and Medicare
| Licence | State | Specialty |
|---|---|---|
| PY00002443 | WA | Cognitive & Behavioral Psychologist primary |
| PY00002443 | WA | Addiction (Substance Use Disorder)… |
| PY00002443 | WA | Clinical Psychologist |
| PY00002443 | WA | Clinical Child & Adolescent Psychologist |
This provider holds licence PY00002443 issued in WA. A licence number in NPPES reflects what was filed at registration — it does not confirm the licence is still active today.
This NPI does not appear in the PECOS Medicare enrolment file. Providers who do not bill Medicare — or who bill only through a group's enrolment — will not appear here. It is not a sign of any problem with the registration.
What Cognitive & Behavioral covers
A psychologist who reflects an experimental-clinical approach distinguished by use of principles of human learning and development and theories of cognitive processing to promote meaningful change in maladaptive human behavior and thinking. NUCC Health Care Provider Taxonomy, code 103TB0200X
All registered taxonomy codes
This provider registers 4 taxonomy codes. The primary code is what appears on most claims; the others record additional recognised specialties.
| Code | Specialty | Licence | State | |
|---|---|---|---|---|
| 103TB0200X | Cognitive & Behavioral Psychologist Cognitive & Behavioral | PY00002443 | WA | primary |
| 103TA0400X | Addiction (Substance Use Disorder) Psychologist Addiction (Substance Use Disorder) | PY00002443 | WA | |
| 103TC0700X | Clinical Psychologist Clinical | PY00002443 | WA | |
| 103TC2200X | Clinical Child & Adolescent Psychologist Clinical Child & Adolescent | PY00002443 | WA |
The taxonomy records how the provider classifies their own practice. It does not confirm which conditions they currently treat, whether they are accepting new patients, or which insurance they take — call the office for that.
Full NPPES record
An NPI-1 identifies a single person. It stays with the clinician for life, even if they move practice or change state, which is why the address on file can lag behind where they actually work today.
| NPI | 1366781932 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Feb 2, 2013 |
| Last updated | Sep 11, 2025 |
| Status | Active |
| Sole proprietor | Yes |
| Credential | PH.D. |
| Practice address |
1493 CAMBRIDGE ST Cambridge, MA 02139 (425) 228-5336 |
| Mailing address |
9609 13TH AVE SW Seattle, WA 98106 |
Number check
How the check works, step by step
Every NPI carries a Luhn check digit — the same scheme used on credit cards. CMS prefixes the number with 80840 before computing it, which marks it as a US health identifier.
| Digit | 8 | 0 | 8 | 4 | 0 | 1 | 3 | 6 | 6 | 7 | 8 | 1 | 9 | 3 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 3 | 3 | 6 | 5 | 8 | 2 | 9 | 6 |
Sum = 68 · next multiple of 10 = 70 · check digit = 2 · actual last digit = 2
A valid check digit only means the number is well-formed. It does not mean the provider is licensed, active, or in good standing — those are separate questions answered by the sections above.