Exhibit 4.13

DESCRIPTION OF THE COMPANY’S SECURITIES

REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES

EXCHANGE ACT OF 1934

Acadia Healthcare Company, Inc. has one class of securities registered under Section 12 of the Securities Exchange Act of 1934, as amended: our common stock, $0.01 par value per share.

In this exhibit, when we refer to “Acadia,” the “Company,” “we,” “us” or “our” or when we otherwise refer to ourselves, we mean Acadia Healthcare Company, Inc., excluding, unless otherwise expressly stated or the context requires, our subsidiaries; all references to “common stock” refer only to common stock issued by us and not to any common stock issued by any subsidiary.

DESCRIPTION OF COMMON STOCK

Our amended and restated certificate of incorporation, as amended, provides that our authorized capital stock consists of 180,000,000 shares of common stock, $0.01 par value, and 10,000,000 shares of preferred stock, $0.01 par value. As of February 26, 2021, there were 89,039,946 shares of our common stock and no shares of our preferred stock issued and outstanding.

This section summarizes the general terms of our common stock. The summaries in this section do not describe every aspect of our common stock. When evaluating our common stock, you should also refer to all of the provisions of our amended and restated certificate of incorporation, our amended and restated bylaws and the Delaware General Corporation Law, as amended (“DGCL”). Our amended and restated certificate of incorporation and our amended and restated bylaws are filed as exhibits to our Annual Report on Form 10-K.

Terms of Common Stock

Voting Rights

Each share of common stock entitles the holder to one vote with respect to each matter presented to our stockholders on which the holders of common stock are entitled to vote. Our common stock votes as a single class on all matters relating to the election and removal of directors on our board of directors and as provided by law. Holders of our common stock do not have cumulative voting rights. Except in respect of matters relating to the election of directors, or as otherwise provided in our amended and restated certificate of incorporation or required by law, all matters to be voted on by our stockholders must be approved by a majority of the shares present in person or by proxy at the meeting at which a quorum is present and entitled to vote on the subject matter. The holders of a majority of the outstanding voting power of all shares of capital stock entitled to vote, present in person or represented by proxy, constitutes a quorum at all meetings of our stockholders. In the case of the election of directors in uncontested director elections, in order to be elected, a majority of the votes cast must be in favor of a nominee’s election. In contested elections, directors must be elected by a plurality of the votes cast.

Dividend Rights

The holders of our outstanding shares of common stock are entitled to receive dividends, if any, as may be declared from time to time by our board of directors out of legally available funds. Our ability to pay dividends on our common stock will be limited by restrictions on the ability of our subsidiaries to pay dividends or make distributions to us, including restrictions under the terms of the agreements governing our indebtedness.

Liquidation Rights

In the event of any voluntary or involuntary liquidation, dissolution or winding up of our affairs, holders of our common stock are entitled to share ratably in our assets that are legally available for distribution to stockholders

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after payment of our debts and other liabilities. If we have any preferred stock outstanding at such time, holders of the preferred stock may be entitled to distribution and/or liquidation preferences. In either such case, we must pay the applicable distribution to the holders of preferred stock, if any, before we may pay distributions to the holders of our common stock.

Other Rights

Our stockholders have no preemptive, conversion or other rights to subscribe for additional shares. All outstanding shares of our common stock are validly issued, fully paid and nonassessable. The rights, preferences and privileges of the holders of our common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of our preferred stock that our board of directors may designate and issue in the future.

Listing

Our common stock is listed on The NASDAQ Global Select Market under the symbol “ACHC”.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Broadridge Corporate Issuer Solutions, Inc.

Registration Rights

Effective December 31, 2015, concurrently with the execution of the sale and purchase deed related to our acquisition of Priory Group No. 1 Limited, we entered into a third amended and restated registration rights agreement (the “Registration Rights Agreement”), with certain members of our current and former management (the “Management Investors”), Waud Capital Partners, L.L.C. (“WCP”), investment funds affiliated with Bain Capital Partners, LLC (collectively, “Bain Capital”) and investment funds affiliated with Advent International Corporation (“Advent”). The Registration Rights Agreement grants certain stockholders “demand” registration rights for registered offerings and “piggyback” registration rights with respect to our securities. Such rights expired for Bain Capital and Advent in connection with their prior sales of Acadia stock. All expenses incident to registrations are required to be borne by us.

Stockholders Agreement

Concurrently with the execution of the merger agreement related to our acquisition of CRC Health Group, Inc. (“CRC”), we entered into an amended and restated stockholders agreement (the “Stockholders Agreement”) with the Management Investors, WCP and Bain Capital. The Stockholders Agreement became effective on February 11, 2015 in connection with the closing of our acquisition of CRC.

The Stockholders Agreement granted WCP certain rights to designate a nominee for election to our board of directors which WCP exercised to designate Reeve B. Waud for election at the annual meeting of stockholders held in 2016 and certain consent rights over the transfer of shares by Management Investors that have expired.

The Stockholders Agreement provides that no Management Investor will take any of the following actions from the date the Company gives notice to the Management Investors that a preliminary or final prospectus has been circulated for a public offering and during the 60 days following the date of the final prospectus for such public offering: (i) offer, sell, contract to sell, pledge or otherwise dispose of, directly or indirectly, any of the Company’s or its subsidiaries’ equity securities or any securities convertible into or exchangeable or exercisable for such securities; (ii) enter into any transaction which would have the same effect as described in clause (i); (iii) enter into any swap, hedge or other arrangement that transfers, in whole or part, any of the economic consequences or ownership of any of the securities described in clause (i); or (iv) publicly disclose the intention to enter into any transaction described in clauses (i), (ii) or (iii). The foregoing restrictions do not apply to transactions made in the subject public offering and those to which the underwriters managing such public offering agree in writing. As used

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in this “– Stockholders Agreement” section, “public offering” refers to any offering by the Company of the Company’s or its subsidiaries’ capital stock or other equity securities to the public pursuant to an effective registration statement under the Securities Act or any comparable statement under any similar federal statute then in force.

Antitakeover Effects of Delaware Law and Acadia’s Amended and Restated Certificate of Incorporation and Amended and Restated Bylaws

Our amended and restated certificate of incorporation and amended and restated bylaws contain provisions that may delay, defer or discourage another party from acquiring control of us. We expect that these provisions, which are summarized below, will discourage coercive takeover practices or inadequate takeover bids. These provisions are also designed to encourage persons seeking to acquire control of us to first negotiate with our board of directors, which we believe may result in an improvement of the terms of any such acquisition in favor of our stockholders. However, they also give our board of directors the power to discourage acquisitions that some stockholders may favor.

Undesignated Preferred Stock

The ability to authorize undesignated preferred stock will make it possible for our board of directors to issue preferred stock with super voting, special approval, dividend or other rights or preferences on a discriminatory basis that could impede the success of any attempt to acquire us. These and other provisions may have the effect of deferring, delaying or discouraging hostile takeovers, or changes in our control or our management.

Classified Board of Directors

In accordance with our amended and restated certificate of incorporation our board of directors is divided into three classes, with each class serving three-year staggered terms. In addition, under the DGCL, directors serving on a classified board of directors may only be removed from the board of directors with cause and by an affirmative vote of the majority of our common stock. These provisions may have the effect of deferring, delaying or discouraging hostile takeovers, or changes in our control or our management.

Requirements for Advance Notification of Stockholder Meetings

In accordance with our amended and restated certificate of incorporation, special meetings of the stockholders may be called only upon a resolution approved by a majority of our board of directors then in office.

Requirements for Nominations and Proposals at Stockholder Meetings

Our amended and restated bylaws prohibit the conduct of any business at a special meeting other than as brought by or at the direction of our board of directors. In accordance with our amended and restated bylaws, nominations of persons for election to our board of directors may be made at a special meeting of stockholders at which directors are to be elected pursuant to the notice of meeting (1) by or at the direction of our board of directors or (2) provided that our board of directors has determined that directors will be elected at such special meeting, by any holder of our stock who (i) is a stockholder of record both at the time the notice is delivered and on the record date for the determination of stockholders entitled to vote at such meeting, (ii) is entitled to vote at the meeting and upon such election, and (iii) complies with the notice procedures set forth in our amended and restated bylaws. These provisions may have the effect of deferring, delaying or discouraging hostile takeovers, or changes in our control or our management.

Stockholder Action by Written Consent

Pursuant to Section 228 of the DGCL, any action required to be taken at any annual or special meeting of our stockholders may be taken without a meeting, without prior notice and without a vote if a consent or consents in writing, setting forth the action so taken, is signed by the holders of outstanding stock having not less than the minimum number of votes that would be necessary to authorize or take such action at a meeting at which all shares of our stock entitled to vote thereon were present and voted, unless the related certificate of incorporation provides

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otherwise. Our amended and restated certificate of incorporation provides that any action required or permitted to be taken by our stockholders may be effected at a duly called annual or special meeting of our stockholders and may not be effected by consent in writing by such stockholders.

Business Combinations with Interested Stockholders

In accordance with our amended and restated certificate of incorporation we are not subject to Section 203 of the DGCL, an anti-takeover law. In general, Section 203 prohibits a publicly held Delaware corporation from engaging in a business combination, such as a merger, with a person or group owning 15% or more of the corporation’s voting stock for a period of three years following the date the person became an interested stockholder, unless (with certain exceptions) the business combination or the transaction in which the person became an interested stockholder is approved in a prescribed manner. Accordingly, we will not be subject to any anti-takeover effects of Section 203 of the DGCL. However, our amended and restated certificate of incorporation contains provisions that have the same effect as Section 203, except that they provide that WCP, any investment fund managed by WCP and any of their respective Affiliates and Associates (each as defined in our amended and restated certificate of incorporation) with whom any of the foregoing are acting as a group or in concert for the purpose of acquiring, holding, voting or disposing shares of our stock and any persons to whom WCP sells at least five percent (5%) of our outstanding voting stock will be deemed to have been approved by our board of directors, and thereby not subject to the restrictions set forth in our amended and restated certificate of incorporation that have the same effect as Section 203 of the DGCL.

Requirements for Amendments to Acadia’s Amended and Restated Certificate of Incorporation and Amended and Restated Bylaws

The DGCL provides that in order to amend the certificate of incorporation, the board of directors must adopt a resolution that then must be approved by the affirmative vote of a majority of the voting power of the outstanding stock entitled to vote thereon, unless a greater vote is specified in the certificate of incorporation, and subject to any additional vote required by any series of preferred stock. In accordance with our amended and restated certificate of incorporation, the articles relating to the following topics may only be amended, altered, changed or repealed by the affirmative vote of the holders of at least a majority of the voting power of all of our outstanding shares of capital stock entitled to vote generally in the election of directors, other than shares of any “Interested Stockholder” (as defined in our amended and restated certificate of incorporation): Board of Directors (Article Six); Limitation of Director Liability (Article Seven); Limitations on Written Consent/Special Meetings (Article Eight); Business Combinations (Article Ten); Poison Pill (Article Eleven); Amendments (Article Twelve); Forum Selection (Article Thirteen); and Severability (Article Fourteen). Our amended and restated certificate of incorporation also provides that Article Nine, which deals with corporate opportunity, may only be amended, altered or repealed by a vote of 80% of the voting power of all of our shares of common stock then outstanding, voting together as a single class. See “—Corporate Opportunity.”

Our amended and restated certificate of incorporation provides that our amended and restated bylaws may be adopted, amended, altered or repealed by the affirmative vote of a majority of our board of directors. In addition, our bylaws may be adopted, amended, altered or repealed by the affirmative vote of the stockholders having at least a majority of the voting power of all of the then outstanding shares of our capital stock, voting together as a single class.

Corporate Opportunity

Our amended and restated certificate of incorporation provides that the doctrine of “corporate opportunity” does not apply against WCP, its affiliates, any investment fund managed by WCP or any of their respective portfolio companies or their respective partners, members, directors, employees, stockholders, agents or successors, in a manner that would prohibit them from investing in competing businesses or doing business with Acadia’s clients or customers. If the ownership of our common stock continues to be highly concentrated, it may prevent you and other stockholders from influencing significant corporate decisions and may result in conflicts of interest that could cause our stock price to decline.

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Limitation on Liability and Indemnification of Officers and Directors

In accordance with our amended and restated bylaws, we must indemnify our directors and officers to the fullest extent authorized by the DGCL and must also pay expenses incurred in defending any such proceeding in advance of its final disposition upon delivery of an undertaking, by or on behalf of an indemnified person, to repay all amounts so advanced if it should be determined ultimately that such person is not entitled to be indemnified.

We entered into indemnification agreements with each of our current directors and executive officers. These agreements require us to indemnify these individuals to the fullest extent permitted under Delaware law against liabilities that may arise by reason of their service to us, and to advance expenses incurred as a result of any proceeding against them as to which they could be indemnified.

The indemnification rights set forth above shall not be exclusive of any other right which an indemnified person may have or hereafter acquire under any statute, provision of our amended and restated certificate of incorporation, our amended and restated bylaws, agreement, vote of stockholders or disinterested directors or otherwise.

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