Net revenue was $11.8 million for the first quarter of 2023, compared to $9.2 million for the first quarter of 2022. The year-over-year increase was driven by the increase in gross systems shipped.
Gross profit for the first quarter of 2023 was $5.1 million, compared to gross profit of $3.7 million for the first quarter of 2022. Gross margin was 43.4% for the first quarter of 2023, compared with 40.2% for the first quarter of 2022. The year-over-year increase in gross margin was primarily due to a reduction in our cost of revenue per unit sold in the first quarter of 2023.
Total operating expenses were $27.9 million, or 236.3% of net revenues, for the first quarter of 2023, compared with $34.1 million, or 371.3%, for the first quarter of 2022. The year-over-year decrease in total operating expenses was primarily driven by lower media spend and lower professional fees, which were impacted by activities related to the previously disclosed Department of Justice investigation and compliance matters in the first quarter of 2022, partially offset by a net increase in personnel and personnel related costs, driven by investments in our compliance, insurance and retail teams, in the first quarter of 2023.
Sales and marketing expenses were $13.4 million, or 113.4% of net revenues, for the first quarter of 2023, compared with $13.3 million, or 144.8%, for the first quarter of 2022. Lower media spend in the first quarter of 2023 compared to the corresponding prior year period was offset by increases in personnel and personnel-related costs.
Research and development expenses were $4.6 million, or 39.0% of net revenues, for the first quarter of 2023, compared with $5.8 million, or 63.7%, for the first quarter of 2022. The year-over-year decrease was primarily driven by lower personnel-related costs and lower third-party costs.
General and administrative expenses were $9.9 million, or 83.9% of net revenues, for the first quarter of 2023, compared with $14.9 million, or 162.8%, for the first quarter of 2022. The year-over-year decrease was primarily driven by a reduction in general corporate costs related to legal, consulting and other professional fees that were driven by activities related to litigation, financing and compliance matters in the first quarter of 2022, partially offset by an increase in personnel and personnel-related costs.
Excluding stock-based compensation expense, non-GAAP operating expenses for the first quarter of 2023 were $24.6 million, including research and development expenses of $4.0 million, sales and marketing expenses of $12.5 million, and general and administrative expenses of $8.1 million. Please refer to the section below titled “Use of Non-GAAP Financial Measures” and the non-GAAP reconciliation tables at the end of this press release.
GAAP loss from operations was $22.8 million, or 193.0% of net revenues, for the first quarter of 2023, compared with $30.4 million, or 331.1% of net revenues, for the first quarter of 2022. The year-over-year decrease in GAAP loss from operations was primarily due to factors described in the above paragraphs. Excluding stock-based compensation expense, non-GAAP loss from operations losses for the first quarter of 2023 were $19.4 million, compared with $27.4 million in the first quarter of 2022.
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